P-type Ge Substrates Research Articles

Layer transfer of ultrathin Ge crystal segregated on Al/Ge(111) structure

Effects of the surface modification by O2 plasma exposure on the Al/Ge(111) structure have been investigated in order to get an insight into a layer transfer technique of the ultrathin Ge layer segregated on the Al/Ge(111) structure toward the device fabrication, and then the wafer bonding of the Al/Ge(111) structure to the thermally-grown SiO2/Si structure has been demonstrated. The O2 plasma treatment and the subsequent pure water rinse were found to be effective to form the hydrophilic surface of the Al/Ge(111) structure with a suppression of the segregated Ge layer oxidation. The Al/Ge(111) structure with the hydrophilic surface was then bonded to the SiO2/Si substrate, and its bonding strength was enough to perform Ge thinning by the chemical mechanical polishing and the wet-chemical etching using H2O2-based solutions. Ohmic contact of the ring-type device pattern with the segregated Ge/Al stack was achieved by using the remaining p-type Ge substrate as the contact pads.

Temperature and doping-dependent interplay between the direct and indirect optical response in buffer-mediated epitaxial germanium

The structural and optical properties of buffer mediated epitaxial germanium (Ge) layer were investigated and compared with bulk n-type and p-type Ge substrates. An interconnected dual-chamber molecular beam epitaxy (MBE) system was used to grow a 280 nm thin Ge epilayer on (100)GaAs substrate with an intermediate AlAs buffer layer. The lattice-matched, abrupt Ge/AlAs heterointerface was analyzed using cross-sectional transmission electron microscopic analysis, and no elemental interdiffusion was detected via secondary ion mass spectrometry. A strong direct gap transition, compared to the indirect gap transition, and a series of phonon-assisted transitions was observed by photoluminescence (PL) spectroscopy. In addition, the intensity of the direct gap recombination decreases with decreasing PL measurement temperatures, which was ascribed to the reduced density of Γ-valley electrons available for recombination at lower temperature. Furthermore, the intensity ratio between the direct and indirect optical transition drastically decreases with decreasing temperature in both n-type epitaxial and p-type bulk Ge. An empirical relation in both direct and indirect peak position with temperature was established. The observed strong luminescence in 280 nm thick epitaxial Ge at room temperature is vital for Ge-based photonic devices. In addition, the quality of the epitaxial Ge layer grown via MBE is on par with bulk Ge substrates.

Effects of pre- and post-microwave annealing treatments on pGe MOS device

Effects of pre- and post- microwave annealing (MWA) treatment on electrical characteristics of p-type Ge substrate (pGe) metal-oxide-semiconductor (MOS) devices were investigated in this work. The physical mechanism was studied with an X-ray photoelectron spectroscopy analysis. The pre-MWA treatment, which is similar to conventional post oxidation annealing on interfacial layer (IL), can passivate the oxygen vacancy by chemisorbed oxygen. The excess chemisorbed oxygen atoms may be left at the interface between IL and high-k, which would induce more interface/oxide traps and form more unstable components in IL. The chemisorbed oxygen can be replaced with well-bonded oxygen by using a post-MWA treatment on high-k dielectric , instead of a conventional post deposition annealing. As a result, pGe MOS device with a double-MWA treatment exhibits low equivalent oxide thickness value (~0.65 nm), small frequency dispersion, low interface trap density, and excellent reliability characteristics without increasing the leakage current. The oxygen vacancy passivation and chemisorbed oxygen suppression with a double-MWA treatment are crucial for high performance Ge MOS device and monolithic 3D IC applications. • The effect of pre- and post- microwave annealing (MWA) treatment is compared. • Oxygen vacancy can be passivated by chemisorbed oxygen in pre MWA. • Excess chemisorbed oxygen can be replaced with well-bonded oxygen by post MWA. • A p-type Ge substrate capacitor can be improved by double MWA.

Characteristic Change of GeO2 / Ge Interface By Hf-Post Metallization Annealing

Si has been widely used as primary semiconductor materials for electronic device fabrication. Due to the limitation of its electrical properties such as electron and hole mobilities, however, Ge would be one of the candidates for future electronic device materials because of its higher mobilities of both carieers. In addition, since Ge is the same Group IV semiconductor as Si, and physical as well as chemical properties are very similar, it can be considered that the manufacturing process of Si semiconductor devices can be followed, and the introduction cost can be suppressed. However, since GeO2 which composed of Ge-O chemical bonds is known to have water solubility and it reacts with Ge substrates at high temperature, it is well known that GeO desorption occurs at GeO2/Ge interface during higher temperature annealing process as well as during oxidation process itself, which causes deterioration of device characteristics. In this research, we attempted to improve interface characteristics by depositing Hf on the GeO2/Ge structure and applying heat treatment (PMA: Post Metallization Annealing). P-type and n-type Ge (100) substrates were cleaned with acetone and ethanol, and native oxide films were removed with dilute-HF dip. GeO2/Ge structure with film thickness of about 20 nm was prepared by thermal oxidation at 500 °C for 30 minutes. A thin metal Hf film was deposited by the sputtering method, and heat treatment was performed at 300 °C for 20 minutes. As the electrode for electrical characteristics measurements, Al films were deposited by vapor deposition, and the interface characteristics and insulating property was evaluated by C-V, TDS and I-V measurement. From C-V characteristics of GeO2 on both n-type and p-type Ge substrates with the measurement frequency of 1MHz, the injection type hysteresis, which means the existence of hole trap site in the GeO2 films adjacent to the GeO2/Ge interface, was observed in samples without PMA. By applying Hf-PMA, the hysteresis width has been drastically decreased. For C-V characteristics with changing the frequency of small AC signal during the measurements, on the other hand, less frequency dispersion can be seen from GeO2/n-Ge structure than that from GeO2/p-Ge samples. The difference of the calculated values of Dit distribution between GeO2/n-Ge and GeO2/p-Ge would be mainly due to the asymmetry of the Dit distribution in the bandgap of Ge, which is caused by the GeO desorption during the thermal oxidation at the GeO2/Ge interface. In fact, it is clearly shown that the decrease ratio in Dit value by the PMA process are almost the same between GeO2/n-Ge and GeO2/p-Ge. From the TDS measurement, GeO desorption starts below 500 °C in samples without PMA, whereas two steps desorption can been seen in that with PMA. Especially, the desorption with higher temperature range start above 600 °C This indicates that it took more energy to release GeO, a slight amount of Hf buried the GeO2 film desorpted GeO by Hf-PMA and the bonding of Ge-O became stronger. From the I-V measurement, we found that the leakage current was reduced and insulating property was improved by applying PMA. The insulating characteristics are more improved at positive bias for p-type and negative bias for n-type. This cause the band barrier of Metal/Oxide was more strengthened, the electron and the hole could not exceed the band barrier. Strengthening the Ge-O bond by applying PMA, the band barrier is also strengthened, and we consider that the leakage current is reduced. It was confirmed that Hf-PMA is effective for both types of Ge substrate as a solution to reduce the Dit values due to the GeO desorption during the oxidation process at the GeO2/Ge interface. For further thinning in the future, it is necessary to optimize the deposition amount of Hf and the PMA temperature and time.

Influence of the atomic layer deposition temperature on the structural and electrical properties of Al/Al2O3/p-Ge MOS structures

The influence of deposition temperature on the structural, chemical, and electrical properties of atomic layer deposition (ALD)-Al2O3 thin films is investigated. ALD-Al2O3 films were deposited on p-type Ge substrates at 80, 150, 200, 250, and 300 °C. The atomic force microscopy analysis reveals smooth and cohesive films with extremely low roughness (0.2–0.6) nm at 150, 200, 250, and 300 °C. On the contrary, Al2O3 films deposited at the lowest available deposition temperature (80 °C) exhibit holes and aggregates implying a nonhomogeneous deposition. The x-ray photoelectron spectroscopy (XPS) analysis indicates the presence of stoichiometric Al2O3 films at all deposition temperatures. The calculated thickness from the analysis of XPS spectra seems to be in good agreement with the ALD nominal thickness for the films deposited at all deposition temperatures except the one of 80 °C. Transmission electron microscopy (TEM) analysis reveals a flat interface between Al2O3 and p-Ge in an atomic level. In addition, TEM and XPS analyses indicate the absence of any oxidized interlayer between p-Ge and Al2O3 films. Furthermore, C-V, G-V, C-f, G-f, and J-V measurements were performed in order to study the electrical properties and evaluate the density of interfacial traps (Dit) of the structures prior and following forming gas annealing procedure. Forming gas annealing clearly improves the electrical response of all tested structures, as expected, by reducing significantly the “streching out” effect and the frequency dispersion at the depletion regime. Leakage currents and Dit in the order of 10−4 A/cm2 (for applied voltage 1 V) and 1011 eV−1 cm−2, respectively, were measured-calculated for all tested structures.

Improvement of Germanium Channel Nmosfet By Using Fluorine Co-Implant Methods

1.Background/ Objectives and Goal Ge has been investigated as a high mobility (both hole and electron) channel material as a substitute for silicon channels in order to boost the device performances. In this paper, we successfully fabricated the Ge nMOSFETs by using fluorine co-implant method. The Ge nMOSFETs by using fluorine co-implant method has good performance with ION/IOFF ratio of ~8.6×103 at VDS = 1V and the subthreshold swing of 382 mV/dec. 2.Methods Fig. 1 illustrates the process steps and structure of our Ge nMOSFETs by using F co-implant methods. We use (100)-oriented p-type Ge wafer with resistivity 0.1~0.6 Ω-cm as the starting material. Firstly, a 400 nm field oxide was deposited on p-type Ge substrates after diluted HF cyclic surface clean. The source/drain regions were defined by photolithography, and subsequently the oxide was etched by BOE. Then a implantation was used to create an n+ source/drain with P and F co-implant at different dose and energy. Following by 100nm SiO2 capping layer, dopant activation with different sequence were accomplished through rapid thermal annealing (RTA) at 600 °C in N2. The split table of dose/energy and RTA sequence was shown in table 1. After defining the active region, a GeO2 (~2 nm) was formed at 520°C for 30 s in pure O2 ambient (~1030 mBar) and then an Al2O3 (5 nm) was covered. 3.ExpectedResults/Conclusion/Contribution Fig. 2 shows the I-V characteristics of co-implant n+-p Ge junction for different annealing sequence, we can observe that the reverse leakage currents of n-Ge contacts decreased. The sequence splits are the P implantation following by annealing at 1 minute and then F implantation following by annealing at 1minute / 2 minutes. It’s obvious that the F could passivate the defect through P implantation by sufficient thermal annealing in the P+F@RTA_1+2min co-implant sample with low reverse leakage current than the P+F@RTA_1+1minsample. Fig. 3 shows the ID-VGS transfer characteristic of the control sample and the P+F@RTA_1+2min co-implant sample of nMOSFETs with W/L =100 μm /10 μm. The measurement voltage were in the linear region at VDS = 0.1 V and the saturation region at VDS = 1 V. We can observe that the co-implant nMOSFET have superior ION current, low IOFF current, ION/IOFF ratio and good subthreshold swing. The ION/IOFF ratio of the co-implant nMOSFET was of ~8.6×103 at VDS = 1V and the subthreshold swing was of 382 mV/dec. The white line cutting is the gate dielectric GeO2 (~2 nm) and Al2O3(5 nm) on top of the Ge substrate. The Ge-nMOSFET and n+-p Ge junction device have been demonstrated by F co-implant methods on p-type Ge substrate. The F implantation can passivate the vacancies in Ge substrate and enhance the overall activated fraction of the dopant in Ge. The shallow junction, low off-state leakage current, and low series resistance could be achieved. Moreover, we also use the best condition to fabricate the Ge n-MOSFET, and superior IONcurrent, low IOFF current, ION/IOFF ratio, good subthreshold swing, and low RSD could be realized. The co-implant methods have great potential for leakage current improvement and shallow junction in the conventional Ge process. REFERENCES [1]M. S. Datta, G. Dewey, M. Doczy, B. Doyle, B. Jin, J. Kavalieros, R. Kotlyar,M. Metz, N. Zelick, and R. Chau, “High Mobility Si/SiGe Strained Channel MOS Transistors with HfO2/TiN Gate Stack,”IEEE International Electron DevicesMeeting,p.28, Dec. 2003 [2]T. Krishnamohan, C. Jungemann, and K. C. Saraswat, “A Novel, Very High Performance, Sub-20 nm Depletion-Mode Double-Gate (DMDG) Si/Si,Ge(l.,jSi Channel PMOSFET,” in IEDM Tech. Dig., 2003, pp. 687-690. Figure 1

Effect of Post Plasma Oxidation on Ge Gate Stacks Interface Formation

One of the key challenges for Ge gate stack is to achieve an improved interface quality between Ge and the high-K dielectric. In order to overcome this limitation, various interface treatments like ozone pre-gate treatment and ozone ambient annealing (1), nitridation of Ge surface (2),formation of a GeO2 layer between Ge and high-K dielectric using ECR plasma technique (3) and formation of an ultra-thin SiO2/GeO2bilayer have been tried. It has recently been reported that slot plane antenna(SPA) microwave plasma treatment helps to improve the EOT and enhances the oxide quality by reducing impurities and leakage current when the dielectric is exposed during or after deposition (4). Moreover SPA oxidation possesses the unique property of having low electron temperature, which makes it a very low damage process compared to other techniques,either inductively coupled plasma(ICP) and electron cyclotron resonance(ECR) plasma (5). In this study we investigated the impact of SPA plasma oxidation (SPAO) treatment in improving the interface quality when MOS capacitors were fabricated on 300mm p-type Ge substrates. SPAO plasma treatments were performed at different steps in the high-k deposition process. The substrate was initially subjected to a dry chemical oxide removal (COR) process. Subsequently, three different sets of samples were prepared with the exposure of SPAO plasma at following locations (Fig.1): CASE-1: SPAO plasma treatment after Al2O3(1nm)/ZrO2(3.5nm) deposition; CASE-2: SPAO plasma treatment was carried out in between Al2O3(1nm) and ZrO2(3.5nm) deposition; CASE-3: the Ge substrate was exposed to SPAO plasma treatment after COR and prior to Al2O3(1nm)/ ZrO2(3.5nm) layer deposition. Al2O3(1nm) and ZrO2(3.5nm) layers were deposited by atomic layer deposition. Capacitance-voltage at multi-frequencies,current-voltage and conductance measurements were performed at room temperature. Parameters like flatband voltage (Vfb), equivalent oxide thickness(EOT), interface state density(Dit),and leakage current were estimated accurately after quantum mechanical corrections and eliminating the series resistance effect. As shown in Fig. 2 lowest fast interface state density is achieved when SPAO plasma treatment was performed after Al2O3 and prior to ZrO2 deposition (CASE-2). A comparable Dit is also observed when plasma exposure was done after the entire gate stack deposition (CASE-1) (Fig.2). From different experimental results significant degradation to both the dielectric quality and interface was observed when SPAO is performed just after COR (CASE-3).

Effects of Carbon Pre-Germanidation Implantation on the Thermal Stability of NiGe and Dopant Segregation on Both n- and p-Type Ge Substrate

In this work, the effects of carbon pre-geramanidation implantation on the thermal stability of NiGe and dopant segregation on both n-type and p-type Ge substrate were investigated systematically. As-prepared NiGe films with carbon pre-germanidation implantation to different doses were characterized by means of sheet resistance measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM), cross-sectional transmission electron microscope (X-TEM) and secondary ion mass spectroscopy (SIMS). The presence of carbon is proved to improve the thermal stability of NiGe formed on both n- and p-type Ge significantly, as well as to lead to dopant segregation (DS) of P and B at the NiGe/Ge interface. The homogeneous distribution of C within NiGe films and stuffing of C atoms at the NiGe/Ge interface is responsible for the enhanced thermal stability of NiGe and DS of P and B during germanidation process.

Electrical and Microstructural Characterization of Cu-Germanide Contacts Formed on p-Type Ge Substrate

We have investigated the electrical and microstructural properties of Cu-germanides formed on p-type Ge substrate as a function of rapid thermal annealing (RTA) temperature. As increasing RTA temperatures, Cu films reacted with Ge and formed Cu-germanides. The Cu3Ge phase appears to be the dominant phase along with Cu5Ge2 phase at annealing temperatures of 500 and 600 °C. The sheet resistance and specific contact resistivity were investigated as a function of germanide formation temperature. A minimum specific contact resistivity value of 6.19´10-6 Wcm2 is obtained after annealing at 400 °C associated with the formation of low stoichiometric Cu3Ge phase. The sheet resistance and specific contact resistivity increased after rapid thermal annealing at temperatures >500 °C, indicated the degradation of the contact properties and could be associated with the formation of copper rich Cu5Ge2 phase and the loss of structural integrity with increasing annealing temperature.

Electrical and Microstructural Characterization of Cu-Germanide Contacts Formed on p-Type Ge Substrate

We have investigated the electrical and microstructural properties of Cu-germanide formed on p-type Ge substrate as a function of rapid thermal annealing (RTA) temperature. As increasing RTA temperatures, Cu films reacted with Ge and formed Cu-germanides. The Cu3Ge phase appears to be the dominant phase along with Cu5Ge2 phase at annealing temperatures of 500 and 600 °C. The sheet resistance and specific contact resistivity were investigated as a function of germanide formation temperature. A minimum specific contact resistivity value of 6.19´10-6 Ωcm2 is obtained after annealing at 400 °C associated with the formation of stoichiometric Cu3Ge. The sheet resistance and specific contact resistivity increased after rapid thermal at temperatures >500 °C indicated the degradation of the contact properties and could be associated with the formation of copper rich Cu5Ge2phase and the loss of structural integrity with increasing annealing temperature.

Components of strong magnetoresistance in Mn implanted Ge

Strong magnetoresistance reaching thousands of percent and non-monotonic field dependent Hall effect were measured in Mn implanted Ge samples in fields up to 60 T and analyzed in the framework of a two carriers model. The measured Hall effect and temperature dependent zero field resistance can be consistently described by parallel conductance along thick p-type Ge substrate with low concentration of highly mobile carriers and along thin Mn doped Ge layer with low mobility carriers. However, the same model is not sufficient to explain experimentally observed suppression of quadratic field dependence of magnetoresistance at low fields and absence of its saturation at high fields. Two additional mechanisms were identified: a strong quasi-linear magnetoresistance of Ge substrate that dominates the low field range and a non-saturating “3/2” power law magnetoresistance of the Mn doped Ge layer dominating the high field range.

InGaAsNSb/Ge double-junction solar cells grown by metalorganic chemical vapor deposition

InGaAsNSb/Ge (1.14/0.67eV) double-junction solar cells have been grown by metalorganic chemical vapor deposition (MOCVD). Ge p–n junction structures are realized by phosphorous diffusion on p-type Ge substrates. GaAs/InGaAsNSb heterojunction structures are grown on the Ge solar cells. The single-junction InGaAsNSb and Ge subcells are electrically connected by a GaAs tunnel junction. The fabricated solar cell exhibits an efficiency of 9.05% under AM 1.5G illumination with an open circuit voltage of 0.92V. The InGaAsNSb subcell possessed a low external quantum efficiency over the sub-GaAs bandgap spectral range, reflecting the short minority carrier diffusion length of the dilute-nitride-antimonide material.

Effective interface passivation of a Ge/HfO2 gate stack using ozone pre-gate treatment and ozone ambient annealing

The physical and electrical properties of a Ge/GeO2/HfO2/Al gate stack are investigated. A thin interfacial GeO2 layer (∼1 nm) is formed between Ge and HfO2 by dual ozone treatments, which passivates the Ge/high-k interface. Capacitors on p-type Ge substrates show very promising capacitance-voltage (C—V) characteristics by using in situ pre-gate ozone passivation and ozone ambient annealing after high-k deposition, indicating efficient passivation of the Ge/HfO2 interface. It is shown that the mid-gap interface state density atthe Ge/GeO2 interface is 6.4 × 1011 cm−2 · eV−1. In addition, the gate leakage current density of the Ge/GeO2/HfO2/Al gate stack passivated by the dual ozone treatments is reduced by about three orders of magnitude compared to that of a Ge/HfO2/Al gate stack without interface passivation.

Probing the properties of atomic layer deposited ZrO2 films on p-Germanium substrates

Zirconium oxide (ZrO2) thin films of 5 and 25 nm thickness were deposited by atomic layer deposition at 250 °C on p-type Ge substrates. The stoichiometry, thickness, and valence band electronic structure of the ZrO2 films were investigated by x-ray and ultraviolet photoelectron spectroscopies. For the electrical characterization, metal-oxide-semiconductor (MOS) capacitive structures (Pt/ZrO2/p-Ge) have been fabricated. Capacitance–voltage and conductance–voltage (C–V, G–V) measurements performed by ac impedance spectroscopy in the temperature range from 153 to 313 K reveal a typical MOS behaviour with moderate frequency dispersion at the accumulation region attributed to leakage currents. For the determination of the leakage currents conduction mechanisms, current density–voltage (J–V) measurements were carried out in the whole temperature range.

Microstructural Evolution and Electrical Characteristics of Er-germanides Formed on Ge Substrate

The microstructural and electrical properties of Er-germanides formed by a solid state reaction between Er and Ge have been investigated at different germanide formation temperatures from 400 to 700°C. Er26Ge23 and Er3Ge4 phases were formed at a germanidation temperature of 400°C, followed by the formation of Er3Ge4 and Er2Ge3 at 500 to 600°C and then ErGe2.16 at 700°C. The sheet resistance gradually decreased with increasing annealing temperature up to 600°C, which could be associated with the phase transformation from Er-rich to Ge-rich Er-germanides. Er-germanides on n-type Ge showed Schottky behavior at low formation temperatures of less than 600°C. Above 600°C they exhibit Ohmic behavior. However, due to strong Fermi level pinning, Er-germanide contact to p-type Ge substrates was demonstrated to be Ohmic regardless of the annealing temperatures. The conversion of Schottky to Ohmic behavior could be attributed to a significant increase in current in the forward and reverse biases caused by the formation of square-shaped microvoids driven by Ge out-diffusion near the interface between germanides and the Ge substrate.

Homoepitaxial growth of germanium for photovoltaic and thermophotovoltaic applications

In the present work homoepitaxial Ge layers were deposited by means of metal organic vapor phase epitaxy (MOVPE) on Ge using iso-butyl germane (iBuGe) as a metal organic precursor. Layers of different thicknesses were grown by varying the deposition temperature between 550 and 700°C on n- and p-type Ge substrates. The films were found to be intrinsically p-type with high carrier concentration, but using AsH3 it was possible to achieve n-type doping. TEM and X-ray diffraction were used to assess the good crystallographic quality of the layers. By depositing a p-type layer onto an n-type Ge substrate or, vice versa, an n-type layer on a p-type Ge substrate is was possible to realize p/n (or n/p) junctions. Mesa structures were realized in order to perform electrical characterizations of the junctions.

Atomically-Engineered Interfaces Between Crystalline-Ge Substrates and i) Nanocrystalline HfO2 and ii) Non-Crystalline Hf Si Oxynitride High-K Dielectrics

This paper presents a spectroscopic study of interfacial bonding and substrate gate dielectric reactions for crystalline Ge-high-K gate dielectric hetero-structures. A novel processing sequence has been developed for i) depositing HfO2 and Hf Si oxynitrides (HfSiON) onto N-passivated Ge(111) and (100) substrates in an attempt to prevent subcutaneous oxidation of the Ge substrate during dielectric deposition, and then ii) eliminating these Ge-N interfacial bonds during 650-800°C rapid thermal annealing in Ar. This approach has been motivated by previous spectroscopic studies which have demonstrated that the band-gaps of GeO2 and Ge3N4 are reduced with respect to their Si counterparts, and cannot be used as interfacial layers (ILs) on n-type Ge substrates, or in n-metal oxide semiconductor field effect transistors (n-MOSFETs) in which a p-type Ge substrate has been inverted. Changes in interface bonding as a function of post-deposition annealing for Ge/HfO2 and HfSiON, and HfO2/HfSiON stacks have been studied by X-ray absorption and photoelectron spectroscopies, revealing i) intrinsic, or pre-existing conduction and valence band edge defects, and ii) process-induced changes in band edge defects as well. [DOI: 10.1380/ejssnt.2009.381]

Elimination of Native Ge Dielectrics at Ge/High-k Dielectric Interfaces for Ge MOS Devices

This paper presents a spectroscopic study of interfacial bonding and substrate gate/dielectric reactions for crystalline Ge-high-K gate dielectric hetero-structures. A novel processing sequence has been developed for (i) depositing HfO2 and Hf Si oxynitrides (HfSiON) onto N-passivated Ge(111) and (100) substrates, designed to prevent subcutaneous oxidation of the Ge substrate during dielectric deposition, and then (ii) eliminating N from Ge-N interfacial bonds during 650-800oC rapid thermal annealing in Ar. This approach has been motivated by spectroscopic studies that have shown that the band-gaps of GeO2 and Ge3N4 are reduced with respect to their Si counterparts and cannot be used as interfacial layers (ILs) either: (i) on n-type Ge substrates, or (ii) in n-MOSFETs in which a p-type Ge substrate is inverted. Changes in interface bonding as a function of post-deposition annealing for G/HfO2 Ge/HfSiON, and Ge/HfSiON/HfO2 stacks have been studied by X-ray absorption and photoelectron spectroscopy revealing (i) conduction and valence band edge defects, as well as (ii) significant process induced changes in these defect densities.

MOVPE growth of homoepitaxial germanium

n-Type Ge epitaxial layers were deposited on p-type Ge substrates by means of metal-organic vapour phase epitaxy (MOVPE) at temperatures ranging from 500 to 600 °C using isobutylgermane (iBuGe) as metal-organic precursor and hydrogen as carrier gas. The samples were grown at different iBuGe partial pressure conditions and were characterised by means of atomic force microscopy (AFM), high-resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The layers grown with iBuGe partial pressure of 3.3×10 −6 bar at 550 °C show a good crystallographic structure, flat surface and a good interface with the substrate, while for lower partial pressures a series of pits was evidenced on the layer. The pit density was found to be dependent on the growth rate. n-Ge/p-Ge diodes, obtained with standard photolitographic techniques, show rectification ratios higher than 10 5 and ideality factors in the 1.008–1.010 range.

Characterization of evaporated selenide semiconductor alloy on p-type substrates

The properties of chalcogenides that are most important for applications as infrared transmitting materials are reported and their mutual relationships are given. Si5Se80In15 films were produced by means of thermal evaporation. The refractive index and the optical energy gap were determined by transmission measurements. Parameters considered in this study are density, molar volume, transition temperatures, electrical properties, infrared transmission, extinction coefficient and refractive index. This composition has no extrinsic and intrinsic absorption between 14 and 20μm and the value of absorption coefficient is estimated lower than 10−3cm−1 at 10.6μm. This glass is also suitable for infrared optical elements. A p–n junction is observed due to evaporated thin film of alloy on p-type Ge substrate.