Planar Doping Research Articles

Composite solders : James L. Marshall, Jose Calderon, Jennifer Sees, George Lucey and Jennie S. Hwang. IEEE Trans. Compon. Hybrids mfg Technol.14(4), 698 (1991)

The InAlAs/InGaAs/InP high electron mobility transistor (HEMT) lattice matched to InP offers excellent high frequency, low noise operation for MMICs and low-noise amplifiers. The InP channel in the InP/InAlAs HEMT offers the advantages of improved high field velocity and higher breakdown voltages (the potential for higher power applications) over InGaAs channel HEMTs. InAlAs has been grown for the first time by CBE using TMAA producing InGaAs/InAlAs and InP/InAlAs HEMTs. Sub-micron InGaAs/InAlAs HEMTs with planar Si doping have been fabricated with ft values of 150 GHz and fmax values of 160 GHz. This device showed excellent pinch-off charateristics, with a maximum transconductance of 890 mS/mm. The planar doped InGaAs channel HEMT had a higher ft than a similar uniformly doped device. However, the non-optimized structure of the planar doped device resulted in a large output conductance of 120 mS/mm, limiting fmax for that device. A sub-micron InP channel device was grown with a quantum well channel and double-sided planar Si doping. A sheet charge density of 4.4×1012 cm-2 and associated room temperature mobility of 2800 cm2/V·s were achieved; however, the saturation current was low. The most likely causes for this are diffusion of the planar doping beneath the channel and the poor quality of the InP on InAlAs interface at the bottom of the quantum well channel.

Sub-micron self-aligned-gate HEMT for microwave applications : H. Schink and R. D. Schnell. Solid-St. Electron.34(11), 1247 (1991)

The InAlAs/InGaAs/InP high electron mobility transistor (HEMT) lattice matched to InP offers excellent high frequency, low noise operation for MMICs and low-noise amplifiers. The InP channel in the InP/InAlAs HEMT offers the advantages of improved high field velocity and higher breakdown voltages (the potential for higher power applications) over InGaAs channel HEMTs. InAlAs has been grown for the first time by CBE using TMAA producing InGaAs/InAlAs and InP/InAlAs HEMTs. Sub-micron InGaAs/InAlAs HEMTs with planar Si doping have been fabricated with ft values of 150 GHz and fmax values of 160 GHz. This device showed excellent pinch-off charateristics, with a maximum transconductance of 890 mS/mm. The planar doped InGaAs channel HEMT had a higher ft than a similar uniformly doped device. However, the non-optimized structure of the planar doped device resulted in a large output conductance of 120 mS/mm, limiting fmax for that device. A sub-micron InP channel device was grown with a quantum well channel and double-sided planar Si doping. A sheet charge density of 4.4×1012 cm-2 and associated room temperature mobility of 2800 cm2/V·s were achieved; however, the saturation current was low. The most likely causes for this are diffusion of the planar doping beneath the channel and the poor quality of the InP on InAlAs interface at the bottom of the quantum well channel.

InAlAs/InGaAs/InP sub-micron HEMTs grown by CBE

The InAlAs/InGaAs/InP high electron mobility transistor (HEMT) lattice matched to InP offers excellent high frequency, low noise operation for MMICs and low-noise amplifiers. The InP channel in the InP/InAlAs HEMT offers the advantages of improved high field velocity and higher breakdown voltages (the potential for higher power applications) over InGaAs channel HEMTs. InAlAs has been grown for the first time by CBE using TMAA producing InGaAs/InAlAs and InP/InAlAs HEMTs. Sub-micron InGaAs/InAlAs HEMTs with planar Si doping have been fabricated with f t values of 150 GHz and f max values of 160 GHz. This device showed excellent pinch-off charateristics, with a maximum transconductance of 890 mS/mm. The planar doped InGaAs channel HEMT had a higher f t than a similar uniformly doped device. However, the non-optimized structure of the planar doped device resulted in a large output conductance of 120 mS/mm, limiting f max for that device. A sub-micron InP channel device was grown with a quantum well channel and double-sided planar Si doping. A sheet charge density of 4.4×10 12 cm -2 and associated room temperature mobility of 2800 cm 2/V·s were achieved; however, the saturation current was low. The most likely causes for this are diffusion of the planar doping beneath the channel and the poor quality of the InP on InAlAs interface at the bottom of the quantum well channel.

ZnS:Mn Electroluminescent Films Prepared by Hot Wall Technique

Manganese-doped zinc sulfide electroluminescent (EL) films were prepared for the first time by a hot wall technique with Mn planar doping. Undoped and Mn-doped ZnS films on glass substrates exhibit preferred cubic (111) orientation at the substrate temperature of 280°C. The Δ2θ value (full width at half-maximum) of the 111 reflection of the ZnS:Mn film in an X-ray diffraction pattern was found to be improved with an increase in Mn concentration and film thickness. By means of secondary ion mass spectroscopy (SIMS) and electron spin resonance (ESR) analyses, it was confirmed that this doping technique was very efficient in obtaining a homogeneous Mn2+ distribution which yielded highly luminescent EL devices. For an optimum device with double insulators of stacked Ta2O5/Al2O3 layers, the maximum luminance and efficiency at 1 kHz sinusoidal excitation were 3200 cd/m2 and 1.3 lm/W, respectively.

Indium doping of CdTe layers and CdTe/Cd 1 − xZn xTe microstructures

Doping of CdTe and Cd 1 − x Zn x Te layers and heterostructures with indium donors during their growth by MBE is described. Characterization by SIMS, electrical measurements and photoluminescence is presented with emphasis on: activation efficiency for uniform and planar doping; degree of localization achieved for step-like doping profiles; doped single and multiple quantum wells. Compensation by acceptor impurities and by intrinsic defects occurs at low (≈ 10 16 cm -3) and at high (< 10 18 cm -3) In concentrations, respectively. Essentially 100% activation efficiency of the donors is achieved in the intermediate range.

Planar doping of p-type ZnSe layers with lithium grown by molecular beam epitaxy

High quality p-type ZnSe layers with hole concentrations of 3 × 10 17 − 1.4 × 10 18 cm -3 have been grown using a planar doping technique employing lithium during molecular beam epitaxy (MBE). The Li-doping is investigated by reflection high energy electron diffraction (RHEED). It is found that islands of Li 2Se are formed on the growing ZnSe surface in the case of heavy Li doping. Secondary ion mass spectroscopy (SIMS) and photoluminescence (PL) are used to characterize the layers grown. SIMS analysis shows an abrupt change in Li concentration at the interface between highly doped (mid 10 19 cm -3) and undoped layers. This is the first report of the successful suppression of Li diffusion. PL spectra at 4.2 K show dominant acceptor-bound exciton emission (I 1). The line shape of I 1 is noticeably broadened with a tail towards the low energy side. This may be explained in terms of a Stark effect on bound excitons arising from charged impurities.

Magnetotransport in planar doping structures

We present the results of magnetostransport measurements on σ-layers in InP. The doping concentrations of the δ-layers covered the range corresponding to the intermediate regime between metallic and dielectric behaviour. Large anisotropy of magnetoresistance and the combination of both quantum and classical Hall effect was observed. The results are discussed in the frame of a simple model.

The Confining Potential for Carriers in Planar Doped GaAs and the Effect of Photoexcitation

ABSTRACTSingle Be and Si δ-doped layers in GaAs have been investigated by Raman spectroscopy. GaAs/AlxGa1-xAs heterointerfaces, placed 30nm from the dopant spike on either side, facilitate optical measurements by the confinement of photogenerated minority carriers. Self-consistent subband calculations have been performed to compute the subband structure of the two-dimensional electron or hole gas which is confined by the space-charge induced potential well at the δ-doping layer. Upon increasing photoexcitation, the increase in density of photocreated electrons in the Be structure is clearly seen in the polarised Raman scattering spectrum by the appearance, and subsequent increase in frequency, of the electron plasmon modes. The electric field at the top GaAs/AlxGa1-xAs interface is monitored by measuring the strength of electric field induced LO phonon scattering.

Effective Si planar doping of GaAs by MOVPE using tertiarybutylarsine

We demonstrate highly effective Si planar doping of GaAs by atmospheric-pressure metalorganic vapor phase epitaxy (MOVPE) using tertiarybutylarsine (tBAs) as an alternative arsenic source. The Si incorporation coefficient using tBAs is always higher than that using arsine. The dependence of the Si incorporation coefficient on the group-V precursor flow rate and the gas flow velocity differs greatly between group-V precursors. This indicates that the gas phase reactions between group-V and dopant source dominate the Si doping process, regardless of group-III precursor. We applied a kinetic simulation to the pyrolysis of group-V precursors and confirmed that a large amount of AsH 2 exists in the gas phase when using tBAs. We propose that the reactions between As species radicals and silane occur, producing silylarsine (H 2AsSiH 3) and that silylarsine is abundant for tBAs. Silylarsine rather than SiH 2 should be the most significant product contributing to the Si doping reactions.

Gas source molecular beam epitaxy growth of heterojunction bipolar transistors containing 1 monolayer δ− Be

We present results on AlGaAs/GaAs Heterostructure Bipolar Transistors containing a 1 monolayer δ-Be doped sheet in a GaAs base 100 Å wide that is grown by gas source molecular beam epitaxy. Also, diffraction measurements performed on 1 monolayer δ-Be layers show the planar doping widths are 40 and 200 Å for gas source and molecular beam epitaxial growth, respectively. Be diffusion measurements versus varying anneal conditions are presented and shown to be consistent with a kick-out mechanism involving interstitial Be.

Comparison of delta doped GaAs grown by MBE and GSMBE using different arsenic species

We have compared the extent of spatial confinement and the optical properties of Be and Si delta doped GaAs grown by gas source and solid source MBE. The delta doped samples were grown at a substrate temperature of 500°C. The two-dimensional doping density we employed in our comparisons was less than 5X10 12 cm −2. Secondary ion mass spectrometry and capacitance-voltage measurements indicate insignificant differences in the spatial distribution of Si and Be for structures grown using As 4, As 2 and AsH 3. Optical measurements indicate that the quality of the doped layers grown with AsH 3 are superior to those grown with solid As source. Our results are explained in terms of defect passivation by H and by the presence of As monomers as the dominant arsenic specie during gas source MBE. We shall also discuss a novel method of obtaining planar doping.

Saturation of Si atom concentration in Si planar-doped InP layers grown by metalorganic chemical vapor deposition

A mechanism which causes saturation in Si atom concentration in planar-doped InP layers was investigated. The layers were grown by atmospheric metalorganic chemical vapor deposition (MOCVD) and planar doping was performed by supplying Si2H6 in PH3 atmosphere. We found that the sheet Si atom concentration of the layers saturated as a function of doping time. We propose a new model which can describe the saturation as competition between adsorption and desorption. This model will describe the doping time dependence and the PH3 flow rate dependence of sheet Si atom concentration of planar-doped InP layers grown by MOCVD.

The Effect of Si Planar Doping on DX Centers in Al.20Ga.74As

ABSTRACTThe effect of planar Si doping on the DX center in AlGaAs is investigated using Capacitance-Voltage and Deep Level Transient Spectroscopy techniques. We observe an increase of approximately six orders of magnitude in the DX center capture cross section in Al.26Ga.74As with planar doped Si spikes of 2×1012cm−2 as compared to conventional homogeneous Si doped Al.26Ga.74As. We also observe a small increase in the DX activation energy which was initiated at a lower planar doping of 4×1011 cm−2 and remained constant for the higher planar doping case. We believe the DX center concentration is not changed by the planar doping levels studied here. A model is proposed to explain the increase in capture cross section based on a biaxial stress state in the planar doped AlGaAs region.

The Effect of Rapid Thermal Annealing on the Electrical and Material Characteristics of Planar Doped and Uniformly Doped GaAs/AiGaAs/InGaAs Pseudomorphic HEMT Structures

ABSTRACTMBE grown GaAs/Al0.25Ga0.75As/In0.85Ga0.85 As structures were subjected to SiNx capped rapid thermal annealing and their electrical and material properties were characterized by Hall measurements and photoluminescence (PL). Low temperature (5°K) PL spectra from undoped structures annealed up to 900°C indicated negligible intermixing at the AIGaAs/lnGaAs interface. For planar doped structures (Nd≈5×1012/cm2) the Hall mobility began to decrease at anneal temperatures as low as 800°C with significant degradation observed for annealing temperatures at 850°C. This data is supported by PL spectra which indicate no significant change for samples annealed at 800°C. For the samples annealed at ≥ 850°C a large increase in the full width at half maximum of the transitions from the electron sub-bands of the InGaAs quantum well were observed, suggesting that the change in electrical characteristics is primarily due to diffusion of the Si doping pulse. In contrast. Hall measurement of uniformly doped structures reveal only small decreases in mobility and no significant change in sheet concentration for anneal temperatures up to 900°C and doping levels up to 2.5×1018/cm3. PL spectra reveal no structural changes.

A new approach for the integration of optoelectronic devices using laser selective area epitaxy

Abstract Laser assisted chemical vapor deposition (LCVD) is a new approach for the integration of optoelectronic devices. Device quality GaAs has been selectively grown in a temperature range of 300–400°C. LCVD films were doped both n- and p-type using H 2 Se and DMZn, respectively. Planar doping with sheet carrier concentrations ranging from 10 12 -10 13 cm -2 and a C-V profile with FWHM of 30Awas achieved. This sharp doping profile, one of the narrowest reported, is a result of the low temperature deposition offered by the LCVD technique. We also report for the first time the direct and selective fabrication of a PIN detector with an external quantum efficiency of 60% (without AR coating) and cutoff frequency of 2 GHz.

Enhancement of mobility in pseudomorphic FETs with up and down monolayers

Summary form only given. A comparison was made between three pseudomorphic FET channels. The control sample was a strained In/sub 0.15/Ga/sub 0.85/As quantum well bounded by undoped Al/sub 0.3/Ga/sub 0.7/As and GaAs with a 50-AA Al/sub 0.3/Ga/sub 0.7/As spacer and 5*10/sup 12/ Si planar doping. The second structure was identical to the first except one GaAs monolayer was replaced with one down monolayer. The third quantum well had one InAs down monolayer and two AlAs up monolayers positioned to increase the intersubband energy between the ground state and the next two states. The mobility was measured as a function of temperature from about 40 to 340 K for these structures. Some results are discussed. >

Characterization of electron irradiation induced defects in δ-doped GaAs superlattice structures

We have studied the behaviour of electron irradiation induced defects in δ-doping GaAs superlattices, using capacitance-voltage and deep level transient spectroscopy. For the planar doping used (10 11SSi cm −2) with a distance of 70 å between each plane, we observed a delocalization of the carriers, in agreement with theoretical calculation. The defects created by the irradiation are identical to the defects created in bulk GaAs. However, we observed in addition two new defects which are tentatively ascribed to a complex formed between the silicon dopant and the arsenic vacancy.

Carbon doping of III–V compounds grown by MOMBE

Recent advances in heterostructure bipolar transistor (HBT) technology have created a need for p-type doping at levels ≥10 20 cm -3. We have achieved p-type doping levels as high as 5×10 20 cm -3 using C, which is introduced through the use of trimethylgallium (TMG) during metalorganic molecular beam epitaxy (MOMBE) growth of GaAs. By utilizing the atomic planar doping method, we have also been able to grow C-doped spikes with hole concentrations as high as 7×10 19 cm -3, with a full width at half maximum of ∼50 Å at 300 K. This level is among the highest reported for planar doping. By switching out the TMG, and switching in the triethylgallium (TEG) to continue to growth of C-free GaAs, we have grown sandwich-type structures with C levels of 10 20 cm -3, which fall off within 210 Å to C levels of <10 17 cm -3. High temperature annealing of such structures reveals a C diffusion coefficient of <10 -16 cm 2 s -1 at 950°C, in agreement with other reports. The electrical properties of layers annealed at high temperatures appear to be influenced by the presence of strain arising from the high C concentration. X-ray diffraction patterns of 3 μm layers doped in excess of 10 20 cm -3 show a lattice constant which corresponds roughly to that calculated by assuming a Vegard law mixture of GaAs and 0.7% GaC. Preliminary results of C-doping of InGaAs will also be discussed. Finally, the usefulness of carbon doping has been demonstrated in ohmic contact formation, Schottky barrier height enhancement in MESFETs and as the base layer in HBTs.

Phase Coherence Length in Planar Doped Thin GaAs Wires Fabricated by Ion Beam Etching

Electrical transport properties have been studied in a film and wires fabricated from a monolayer doped or a homogeneously doped thin GaAs by mesa etching techniques. The dependence of the electron wave coherency upon the wire widths and fabrication processes is investigated from their low-temperature behavior of the phase coherence length Lφ derived from the nagative magnetoresistance and the amplitude of the conductance fluctuations. Low-temperature saturations of Lφ occur only in narrow wires. This suggests that Lφ is affected by the ion beam induced damage within the mesa side walls. A difference in Lφ between reactive ion-beam-etched and ion-milled wires is explained by the decrease of the diffusion constant. The corresponding difference in the conductance fluctuation amplitudes is larger than that expected from the difference in Lφ.

Photoluminescence studies of planar-doped AlxGa1-xAs

The authors report near band edge photoluminescence measurements of Si-doped AlxGa1-xAs(x=0.32) using the planar doping technique in which the carrier density per plane n2DEG varies from1011 cm-2 to 2*1013 cm-2. The study reveals that the DX related luminescence band is only detected for low doping densities, and that an autocompensation mechanism occurs at high doping densities.