P-type Ge Research Articles

High performing ITO/Ge heterojunction photodetector for broad wavelength detection

High-performing photodetector was fabricated by the ITO/Ge heterojunction device. Due to a small bandgap Ge semiconductor, ITO/Ge photodetector showed a significantly high photoresponse for long wavelengths. For ITO/Ge photodetector fabrication, an optically transparent and electrically conductive ITO layer was deposited on a Ge substrate and spontaneously formed a rectifying junction. The HRTEM image revealed the presence of GeOx at the interface of the ITO and Ge. The XPS and UPS studies were carried out to realize the band-offset structure of ITO/Ge photodiode. When the p-type Ge and ITO are brought into contact, the Fermi levels of both the materials are lined up. Besides, the energy bands of Ge are pinned to the Fermi level of the ITO layer at the junction. The band bending effect is depicted from the band offset of the ITO/Ge photodetector. We discuss an effective method of the ITO/Ge heterojunction device fabrication and suggest a strong route for high-performing broad range wavelength (600–900 nm) photodetectors.

Magnetotransport in p-type Ge quantum well narrow wire arrays

We report magnetotransport measurements of a SiGe heterostructure containing a 20 nm p-Ge quantum well with a mobility of 800 000 cm2 V−1 s−1. By dry etching arrays of wires with widths between 1.0 μm and 3.0 μm, we were able to measure the lateral depletion thickness, built-in potential, and the phase coherence length of the quantum well. Fourier analysis does not show any Rashba related spin-splitting despite clearly defined Shubnikov-de Haas oscillations being observed up to a filling factor of ν = 22. Exchange-enhanced spin-splitting is observed for filling factors below ν = 9. An analysis of boundary scattering effects indicates lateral depletion of the hole gas by 0.5 ± 0.1 μm from the etched germanium surface. The built-in potential is found to be 0.25 ± 0.04 V, presenting an energy barrier for lateral transport greater than the hole confinement energy. A large phase coherence length of 3.5 ± 0.5 μm is obtained in these wires at 1.7 K.

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.

High-Electron-Mobility SiGe on Sapphire Substrate for Fast Chipsets

High-quality strain-relaxed SiGe films with a low twin defect density, high electron mobility, and smooth surface are critical for device fabrication to achieve designed performance. The mobilities of SiGe can be a few times higher than those of silicon due to the content of high carrier mobilities of germanium (p-type Si: 430 cm2/V·s, p-type Ge: 2200 cm2/V·s, n-type Si: 1300 cm2/V·s, and n-type Ge: 3000 cm2/V·s at 1016per cm3doping density). Therefore, radio frequency devices which are made with rhombohedral SiGe onc-plane sapphire can potentially run a few times faster than RF devices on SOS wafers. NASA Langley has successfully grown highly ordered single crystal rhombohedral epitaxy using an atomic alignment of the[111]direction of cubic SiGe on top of the[0001]direction of the sapphire basal plane. Several samples of rhombohedrally grown SiGe onc-plane sapphire show high percentage of a single crystalline over 95% to 99.5%. The electron mobilities of the tested samples are between those of single crystals Si and Ge. The measured electron mobility of 95% single crystal SiGe was 1538 cm2/V·s which is between 350 cm2/V·s (Si) and 1550 cm2/V·s (Ge) at 6 × 1017/cm3doping concentration.

Direct estimation of capture cross sections in the presence of slow capture: application to the identification of quenched-in deep-level defects in Ge

Quenching experiments have been performed on both n- and p-type Ge in a dedicated furnace using infrared lamp heating. The capture and emission characteristics of the induced deep-level defects in the quenched samples were investigated by means of deep level transient spectroscopy. For all defect levels, a high impact of capture in the transition region (slow capture) was found. An empirical approach to analyse this effect is presented, which allows to extract reliable capture cross section parameters. The defect parameters thus obtained were compared with previously published data and it was found that some prominent quenching-induced deep levels are related to metal impurities (Cu and Ni), while others may be vacancy-related.

Influence of delta-doping on the hole capture probability in Ge/Si quantum dot mid-infrared photodetectors.

We study the effect of delta-doping on the hole capture probability in ten-period p-type Ge quantum dot photodetectors. The boron concentration in the delta-doping layers is varied by either passivation of a sample in a hydrogen plasma or by direct doping during the molecular beam epitaxy. The devices with a lower doping density is found to exhibit a lower capture probability and a higher photoconductive gain. The most pronounced change in the trapping characteristics upon doping is observed at a negative bias polarity when the photoexcited holes move toward the δ-doping plane. The latter result implies that the δ-doping layers are directly involved in the processes of hole capture by the quantum dots.

Band alignment study of lattice-matched In0.49Ga0.51P and Ge using x-ray photoelectron spectroscopy

Lattice-matched In0.49Ga0.51P was grown on a p-type Ge(100) substrate with a 10° off-cut towards the (111) by low temperature molecular beam epitaxy, and the band-alignment of In0.49Ga0.51P on Ge substrate was obtained by high resolution x-ray photoelectron spectroscopy. The valence band offset for the InGaP/Ge(100) interface was found to be 0.64 ± 0.12 eV, with a corresponding conduction band offset of 0.60 ± 0.12 eV. The InGaP/Ge interface is found to be of the type I band alignment.

High-Mobility MOSFETs Fabricated on Continuous, Wafer-Scale Ge Films Epitaxially Grown on Si

We report the material characterization of continuous, wafer-scale Ge films epitaxially grown on Si by molecular beam epitaxy. The material quality of Ge is further tested by fabricating high-mobility, long-channel MOSFETs. Our growth technique makes use of a thin chemical SiO 2 template with nanoscale windows and carefully timed thermal annealing during the initial stage of island coalescence. The resulting defect density in n- and p-type Ge is ~2 × 10 5 and 5 × 10 7 cm -2 . The MOSFETs are then fabricated on these substrates, where the gate-stack consists of Ti/HfO 2 /GeO x N y /Ge-on-Si. The GeO x N y interlayer is used to effectively passivate the Ge surface. The subthreshold slope is ~100 and ~200 mV/decade for p- and n-MOSFETs, compared with ~80 mV/decade for p-MOSFETs built on bulk-Ge substrates. The p- and n-MOSFETs also show enhanced peak effective hole and electron mobilities of 400 and 950 cm 2 /V-s that are 82% and 30% increase over the universal mobilities in Si.

Fermi-Level Depinning of Ge Schottky Junction Using Se Treatment

Depinning of the Fermi-level at metal/Ge Schottky junctions was achieved by Se treatment at room temperature. Due to the strong Fermi-level pinning close to the valence band edge in Ge, Schottky and Ohmic behaviors were observed in conventional Al Schottky contact s to n- and p-type Ge, respectively. However, Al Schottky contacts to n- and p-type Ge with Se treatment became Ohmic and Schottky, respectively. The transmission electron microscopy (TEM) examination combined with X-ray photoemission spectroscopy (XPS) analysis showed that Se treatment at room temperature yielded the formation of a fairly uniform Se-Ge alloy film with partially ionic binding nature caused by the chemical reaction between Se and Ge. This led to the reduction of surface states of Ge surface along with the passivation of dangling bonds by the incorporation of Se atoms, which was responsible for Fermi-level depinning at Al/Ge junctions.

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.

Fermi-Level Depinning of Ge Schottky Junction Using Se Treatment

Depinning of the Fermi-level at metal/Ge Schottky junctions was achieved by Se treatment at room temperature. Due to the strong Fermi-level pinning close to the valence band edge in Ge, Schottky and Ohmic behaviors were observed in conventional Al Schottky contacts to n- and p-type Ge, respectively. However, Al Schottky contacts to n- and p-type Ge with Se treatment became Ohmic and Schottky, respectively. Electron and hole barrier heights calculated using Richardson plots were found to be 0.15 eV for of Al contacts to Se-treated n- type Ge, and 0.33 eV for Al contacts to Se-treated p-type Ge, respectively. The transmission electron microscopy (TEM) examination combined with X-ray photoemission spectroscopy (XPS) analysis showed that Se treatment at room temperature yielded the formation of a fairly uniform Se-Ge alloy film with partially ionic binding nature caused by the chemical reaction between Se and Ge. This led to the reduction of surface states of Ge surface along with the passivation of dangling bonds by the incorporation of Se atoms, which was responsible for Fermi-level depinning at Al/Ge junctions.

Spin Transport in Ge Nanowires for Diluted Magnetic Semiconductor-Based Nonvolatile Transpinor

Spintronic devices, in particular spin field-effect transistors (spinFETs), have been studied for decades as a promising candidate to replace Si CMOS devices. Several variants of spinFETs have been proposed to use the spin of electrons as another degree of freedom for information processing. However, all the previous proposals still use charge current, which generates power dissipation. To eliminate the charge current, we propose a novel spin-based transistor (transpinor) based on diluted magnetic semiconductor (DMS) with electric field-controlled paramagnetism-to-ferromagnetism phase transition. One promising prototype is to integrate a MnxGe1-x DMS nanowire, whose ferromagnetism can be effectively controlled by a gate electrode, with Mn5Ge3ferromagnetic contacts for spin injection (Figure 1). Another variant of the ferromagnetic contacts could be epitaxial Fe/MgO tunnel junctions. In this transpinor device, the magnetic moments are transferred from the source to the channel, and then to the drain through spin injection and exchange interaction. As the gate electrode manipulates the ferromagnetism of the DMS channel, it controls the communication between the source and drain.In order to realize the proposed transpinor device, we first studied the spin transport in Ge nanowires and demonstrated the electrical spin injection and detection using both ferromagnetic Mn5Ge3 Schottky contacts and Fe/MgO tunnel junctions (Figure 2). The Mn5Ge3 contacts were fabricated by germanidation through rapid thermal annealing. This convenient approach produced single-crystalline Mn5Ge3 contacts with a controlled channel length and atomically clean interfaces to the Ge nanowire, which helped alleviate Fermi level pinning at the interface. Subsequently, electrical spin injection and detection was successfully demonstrated in the Mn5Ge3/Ge/Mn5Ge3 nanowire transistor. A spin diffusion length of λsf = 480 nm and a spin flip lifetime of τsf = 244 ps are revealed in p-type Ge nanowires at T = 10 K, which were much larger than those reported for bulk p-type Ge. Meanwhile, spin injection into Ge nanowires with epitaxial Fe/MgO tunneling contacts was performed in nonlocal spin valve measurements. The spin diffusion length of λsf = 2.57 μm and the spin lifetime of τsf = 7.2 ns were obtained in n-type Ge nanowires at T = 40 K, which are again much larger than those in bulk n-type Ge. The significant enhancement in the spin lifetime and diffusion length in nanowires suggested that the spin relaxation was suppressed in nanowires compared with bulk materials.Furthermore, we successfully demonstrated the pattern-assisted growth of MnxGe1-x DMS nanowires (Figure 3), which serve as the transpinor channel. The growth was performed using molecular beam epitaxy (MBE) chamber with SiO2 nanotrenches as the mask. The ferromagnetic MnxGe1-xnanowires showed a Curie temperature above 400 K without any precipitate. The ferromagnetism can be further modulated by a gate voltage at 100 K in a metal-oxide-semiconductor capacitor structure, demonstrating electric field control of ferromagnetism. This result, along with the electrical spin injection into Ge nanowires, lays the foundation to build the transpinor device as a possible realization of all-spin logic devices with built-in memory for low-power applications. Acknowledgement: This work was in part supported by Western Institution of Nanoelectronics (WIN) and National Science Foundation through grant ECCS 1308358.

Mn Related Defect Levels in Germanium

1. Introduction. Mn doped germanium was studied almost 60 years ago by means of Hall effect [1] and photo conductivity [2] measurements. Based on the temperature dependence of the resistivity and carrier concentration, two levels, one at 0.37eV from the conduction band and one at 0.16eV from the valence band have been assigned to Mn impurities[1]. In agreement with the valence bond model and similar observations by counterdoping with donors for Fe, Co and Ni, these impurities have been assigned to double acceptors. Moreover, the presence of a double acceptor level was confirmed by the observation of the Mn2- state with Electron Paramagnetic Resonance (EPR). [3] However it was also noted in the early studies that the presence of contamination with acceptor impurities may cast doubt on the charge transition assignment. Since the availability of Deep Level Transient Spectroscopy (DLTS), which is a more reliable technique to study deep levels in semiconductors, the electronic properties of most of the 3d transition metals have already been studied with a higher energy resolution. Metal in-diffusion was successful to introduce Cu and Ni[4]. More recently the defect levels of Ti, Cr, Fe and Co have been identified with DLTS on metal-implanted Ge [5,6]. The present study reports on results obtained on Mn doped Ge. 2. Experimental conditions. The source material are single crystal germanium wafers, supplied by Umicore, with a shallow dopant concentration of 1014 cm-3 Ga and Sb for p- and n-type, respectively. To introduce Mn impurities, 99.995% pure Mn was thermally evaporated on the Ge surface. Afterwards the specimens were placed in a resistive furnace under Ar atmosphere for 10 minutes at 700°C. Finally, the residual Mn on the surface was removed by etching with a mixture of HNO3 and HF (3:1?). Schottky diodes for DLTS were prepared by evaporation of Au (n-type) or In (p-type) barriers immediately after etching. To identify the contamination introduced during the processing, Schottky diodes were also prepared on parts of the specimens outside the Mn covered areas. Schottky diodes on n-Ge were also prepared by annealing the n-Ge:Mn samples (after indiffusion at 700°C) to 400°C for 20 min in order to form a MnGe metallic alloy contact. 3. Results and discussion. Fig. 1 a shows the DLTS spectrum of n-Ge:Mn with a MnGe Schottky contact. A similar spectrum was recorded on the specimen with an Au-Schottky barrier. Conventional DLTS shows one electron trap (Mn-E1), while injection of minority carriers (Vp>0) reveals two additional levels (Mn-H1 and Mn-H2). Fig. 1 b shows the DLTS spectrum of p-type Ge, with presence of Mn-H1 and Mn-H2 only after Mn diffusion.Figure 1: DLTS spectrum of a) n-Ge/MnGe diode. b) p-type Ge with and without Mn-difussion. The electron trap Mn-E1 (E=0.36eV) and the hole trap Mn-H1 (E=0.14eV) correspond with the two levels reported before [1,2]. The Mn-H2 peak (E=0.34eV) has to our knowledge not been reported before in the context of transition metal impurities. Nonetheless, its appearance only in Mn diffused samples, its almost equal amplitude and concentration profile to Mn-H1 suggests that it is also related to substitutional Mn in Ge. This may indicate that the substitutional Mn defect can adopt 4 charge states in Ge, one of which certainly corresponds with 2-, as identified with EPR. 4. Conclusions. Three Mn related defect levels have been identified with DLTS. The striking similarity with previously published results for two of the observed levels suggest the assignment to substitutional Mn in germanium. The third level was not reported before but can most probably also be assigned to Mn.

Investigation of Al-PMA Effect on Al2O3/GeOX/Ge Gate Stack

To realize high mobility Ge channel metal-oxide-semiconductor field-effect transistor (MOSFET), formation of gate stack with low interface state density (D it) is extremely important. Recently, it has been reported that Al2O3/GeOX/Ge gate stack fabricated by atomic layer deposition (ALD) and plasma post oxidation using electron cyclotron resonance (ECR) had obtained low D it less than 1011 eV-1cm-2 [1]. On the other hand, our group has previously reported that Al introduction into SiO2/GeO2/Ge gate stack by post metallization annealing (Al-PMA) is effective to decrease both D it and slow trap in the lower half of the band gap [2,3]. If Al-PMA is also effective on Al2O3/GeOX/Ge, it will be a useful method to improve MOSFET performance. In this study, we investigated Al-PMA effect on Al2O3/GeOX/Ge gate stack. Ge-MOS capacitors were fabricated by the following procedure. First, a p-type (100) Ge substrate was dipped in dilute HF solution to remove native oxides. Then 1 nm-Al2O3 was deposited at 300°C using ALD. Subsequently, ECR plasma post oxidation was carried out at RT for 1 min. The oxidation conditions were microwave power of 500 W, gas pressure of 1.15×10-1 Pa, and O2/Ar flow rate of 3/18 sccm. Then 4.1 nm-Al2O3 and 1 nm-SiO2 were deposited using ALD and rf magnetron sputtering, respectively. Subsequently, post deposition annealing (PDA) was carried out at 400°C for 30 min, and 100 nm-Al as a gate electrode was deposited by vacuum evaporation. Al-PMA was carried out at 400°C for 30 min. Finally, the electrode was patterned with an area of 2.25×10-4 cm2. For a comparison, the MOS capacitor without Al-PMA was also prepared. Figures 1 and 2 show C-V and J-V characteristics of two types of samples, respectively. The equivalent oxide thickness (EOT), hysteresis (HT), flat band voltage (V fb), and effective breakdown field (E B) are summarized in Table 1. We can find that V fb is significantly shifted to the positive direction by Al-PMA. This is considered the effect of interface dipole. Generally, it is known that dipole is formed at high-k/SiO2 interface [4-7]. Therefore, the dipole is also created at the 1 nm-SiO2/4.1 nm-Al2O3 interface, leading to negative shift of V fb [7]. From the reduction of EOT by Al-PMA, it is considered that Al near the Al/SiO2 interface was oxidized, and changed to Al2O3. As a result, the dipole which is the opposite direction of one described above is formed, leading to positive shift of V fb. We can also find that HT is remarkably reduced by Al-PMA. It agrees well with the previous study of SiO2/GeOX system [2], suggesting that reduction of D it and/or slow trap by Al introduction to the gate insulator. On the other hand, low leakage current has been maintained even after Al-PMA. Figure 3 shows energy distributions of D it estimated by deep level transient spectroscopy [3]. It is clearly observed that both D itand slow trap in the lower half of the band gap are reduced by Al-PMA. From the results mentioned above, we can conclude that Al-PMA is also effective for Al2O3/GeOX/Ge gate stack similar to SiO2/GeOX/Ge. We will report Al-PMA effect for Ge p-MOSFET at the conference.

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.

Characterization of Chemical Bonding Features and Interfacial Reactions in Ge-MIS Structure with HfO2/TaGexOy Dielectric Stack

Control of the chemical reactions at both high-k/Ge and metal/high-k interfaces is of great importance to realize the high quality Ge-MIS capacitor with a thinner EOT. So far, we have fabricated Ge-MIS structures with HfO2/TaGexOy gate stack, in which TaGexOy is used as an interfacial control layer between HfO2 and Ge substrate from the viewpoint of relatively high dielectric constant (ε = ~9ε0), and CET of 1.4 nm has been obtained [1]. As for the metal/dielectric interface, it has been clarified that thermally grown GeO2 are reduced depending on element metals formed by thermal evaporation, and this reduction reaction reflects the Gibbs free energy difference [2, 3]. In this work, we mainly focused on the chemical reactions in the TiN/HfO2/TaGexOygate stack caused by post metallization annealing (PMA), and the chemical structures of the MIS samples were examined by using hard x-ray photoemission spectroscopy (HAXPES) excited synchrotron radiation (hν = 7939 eV).A 2 nm-thick TaOx layer was deposited on wet-cleaned p-type Ge(100) surface at 400 ºC in a layer-by-layer fashion in which Ta-TTT was introduced intermittently using a N2 bubbling method. Subsequently, a ~2 nm-thick HfO2 layer was deposited at 280 ºC by an ALD method using TEMA-Hf and O3. Then, the post deposition annealing (PDA) was performed at 400 °C in diluted O2 ambience to densify the dielectrics. A formation of the TaGexOy interfacial layer by PDA was confirmed from XPS analyses. After that, a TiN thin layer with a typical thickness of ~15 nm was deposited by RF sputtering. In some samples, PMA in the temperature range from 300 to 600 °C was carried out in N2ambience at atmospheric pressure.Figure 1 shows the HAXPES core-line signals taken for TiN/HfO2/TaGexOy/Ge structure before and after PMA. Although a slight increase in the chemically shifted Ge 2p3/2 signals due to the incorporation of Ge atoms into high-k dielectric layers was observed after PMA at 400 °C, change in the chemical structure near the interface between TiN and HfO2/TaGexOy dielectrics were hardly detected. Even in the reference sample of TiN/GeO2(21nm)/Ge structure, chemical bonding features at the top interface show a good thermal stability against PMA at 400 °C. After the PMA at temperatures over 500 ºC, chemically shifted Ge 2p3/2 signals were drastically increased. From the photoelectron take-off angle dependence of core-line signals for the sample after PMA at 600 °C, the formation of Ge oxide component was confirmed at the sample surface. In contrast, significant diffusion of Hf atoms into TiN was hardly detected. Electrical properties of MIS capacitors also show a significant increase in the gate leakage current and a decrease of accumulation capacitance by PMA at temperatures over 500 ºC. These results suggest that dissociation of Ge-O bonds proceeds in the region near the TiN at temperatures over 500 ºC and it makes a degradation of the electrical properties.AcknowledgementsThis work was supported in part by JSPS Core-to-Core Program of International Collaborative Research Center on Atomically Controlled Processing for Ultralarge Scale Integration. The Ta-TTT precursor was provided by TOSOH Corporation. A part of this work was supported by Research Institute for Nano-device and Bio Systems (RNBS), Hiroshima University, Japan. HAXPES experiments were done at a beam line of BL47XU in SPring-8 with the approval of JASRI as a Nanotechnology Support Project of the Ministry of Education, Culture, Sports, Science, and Technology (Proposal No. 2013A1696/BL47XU). We would like to thank Prof. S. Higashi (Hiroshima Univ.) and Dr. E. Ikenaga (JASRI) for the fruitful discussion and contribution in assisting the experiments.

Phosphorous ion implantation into NiGe layer for Ohmic contact formation on n-type Ge

Low-resistivity Ohmic contacts on n-type germanium (Ge) together with ideal rectifying characteristics for p-type Ge were achieved using phosphorous-ion-implanted nickel germanide (NiGe). A pre-germanidation process prior to ion implantation was employed, and subsequent drive-in annealing at low temperature was used to precisely control the phosphorous profile and optimize the process conditions. Very low contact resistance on n-type Ge was demonstrated by using low-temperature drive-in annealing at 300 °C. Further process optimization (ion dose of 2 × 1015 cm−2; drive-in annealing at 400 °C for 30 min) resulted in an effective electron Schottky barrier height as low as 0.09 eV for n-type Ge and an on/off current ratio of five orders of magnitude for p-type Ge. The proposed low-temperature contact formation process offers a significant advantage in source/drain contact formation for Ge-based high mobility n-channel transistors.

Modeling 20-nm Germanium FinFET With the Industry Standard FinFET Model

In this letter, we present modeling results for germanium p-type FinFETs using the industry standard Berkeley Spice Common Multi-gate Field Effect Transistor (BSIM-CMG) model. The effect of perpendicular electrical field on hole mobility in germanium FinFETs is found to be different from silicon FinFETs. We present an updated Ge mobility equation to account for this difference. With this single update, BSIM-CMG agrees very well with the measured <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I-V</i> data of Ge FinFETs with a gate-length from 130 to 20 nm. We conclude that a production quality standard model is available for simulation of circuits employing p-type Ge FinFET.

Erratum to: “Influence of the nonequilibrium-carrier concentration on the Hall voltage in a p-type semiconductor”

The dependence of the Hall voltage on the external electric field in a p-type semiconductor sample placed in a weak magnetic field is investigated. It is shown that the Hall voltage depends nonlinearly on the electric field in a sample whose thickness is comparable to the diffusion length and surface-recombination velocity is rather small. The Hall-voltage sign is opposite to that in a bulk sample in a certain range of electricfield strengths. The theoretical model describes well the experimental data for a p-type Ge sample.

Reliable reduction of Fermi-level pinning at atomically matched metal/Ge interfaces by sulfur treatment

This study demonstrates that by using a sulfur (S) treatment on the Ge surface, a reduction in Fermi level pinning can reproducibly be achieved at atomically matched metal/Ge(111) interfaces. The Schottky barrier height for p-type Ge can be controlled by changing the metal work function despite the metal/Ge junctions. The results indicate that the combination of atomic-arrangement matching and S treatment can remove extrinsic factors influencing Fermi level pinning at metal/Ge interfaces.