ECR plasma etch fabrication of C-doped base InGaAs/InP DHBT structures: A comparison of CH4/H2/Ar vs BCl3/N2 plasma etch chemistries

We compare ECR plasma etch fabrication of self-aligned thin emitter carbondoped base InGaAs/InP DHBT structures using either CH₄/H₂/Ar or BCl₃/N₂ etch chemistries. Detrimental hydrogen passivation of the carbon doping in the base region of our structure during CH₄/H₂/Ar dry etching of the emitter region is observed. Initial conductivity is not recovered with annealing up to a temperature of 500°C. This passivation is not due to damage from the dry etching or from the MOMBE growth process, since DHBT structures which are ECR plasma etched in BCl₃/N₂ have the same electrical characteristics as wet etched controls. It is due to hydrogen implantation from the plasma exposure. This is supported with secondary ion mass spectroscopy profiles of structures which are etched in CH₄/D₂/Ar showing an accumulation of deuterium in the C-doped base region.     

电感耦合等离子体刻蚀InP端面的掩膜特性研究

深入研究了掩膜制作工艺对电感耦合等离子体刻蚀的InP端面的影响。首先比较了光刻胶、SiO2和Si3N4三种材料的掩膜特性，发现掩膜图形的致密性、侧壁粗糙度和垂直度等对刻蚀效果具有至关重要的影响。然后通过优化SF6等离子体刻蚀Si3N4的条件，得到了边缘平整且侧壁垂直的掩膜图形。利用这一掩膜制作技术，获得了深度达7μm的光滑垂直的InP刻蚀端面，选择比达15：1。     

Interface structure in arsenide/phosphide heterostructun grown by gas-source MBE and low-pressure MOVPE

We have used cross-sectional scanning tunneling microscopy (STM) to study interface structure in arsenide/phosphide heterostructures grown by gas-source molecular beam epitaxy (GSMBE) and by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). High-resolution images of GSMBE samples consisting of GaAs interrupted at 200Å intervals with a 40 s P₂ flux reveal substantial, growth-temperature-dependent incorporation of phosphorus with nanometer-scale lateral variations in interface structure. STM images of InGaAs/InP multiple quantum well structures grown by LP-MOVPE show evidence of interface asymmetry and extensive atomic cross-incorporation at the interfaces. Data obtained by STM have been corroborated by high-resolution x-ray diffraction and reflection high-energy electron diffraction. Together, these studies provide direct information about nanometer-scale grading and lateral nonuniformity of arsenide/phosphide interfaces that can occur under these growth conditions.     

The organometallic vpe growth of GaSb and GaAsl−xSbx using trimethylantimony

The organometallic vapor phase epitaxial (OMVPE) growth of GaSb and GaAs_l−xSb_x (0 ≤ × ≤ 0.26, 0 .64 ≤ × ≤1) is discussed. Trimethylgallium and trimethylantimony are used as the Ga and Sb source, respectively. Most GaAs_1× Sb_x growths are done using arsine, but the use of an alternate arsenic source, trimethylarsenic, is also discussed. In contrast to most arsenic-containing alloys, both GaSb and Sb-rich GaAs_1−x Sbx are grown under Group III-rich conditions. The total input flux as well as the ratio of the input chemicals must be closely regulated. In particular, growth of GaAs_l−xSb_x requires careful control of the trimethylantimony-to-total Group V ratio, since arsenic preferentially incorporates into the crystal. This work was supported by DOE through the Division of Materials Science Branch of the Office of Basic Energy Sciences under Contract No. DE-AC03-79SF10610.     

Electron effective mass in InuGa1−uPvAs1−v for 0 ≤ v ≤ 1

The electron effective mass in In_uGa_1−uP_vAs_1−v has been measured on seven samples lattice-matched to InP and evenly spaced in values of v between 0 and 1, using the temperature dependence of the amplitude of the Shubnikov-de Haas oscillations at high magnetic fields. Values of the carrier concentrations, Hall mobilities and Dingle temperatures measured on these samples are also reported. Work sponsored in part by the National Science Foundation, Grant No. ENG 76-09586, and in part by International Telephone and Telegraph Electro-Optical Products Division. Work done in part at the M.I.T. Francis Bitter National Magnet Laboratory. Funded in part by the National Science Foundation under Grant No. DMR-76-80895.     

LOW TEMPERATURE OPEN TUBE Zn DIFFUSION IN InP/InGaAs(P)

To fabricate quasi-planar optoelectronic integrated circuits(OEICs),a new open tube Zndiffusion method has been developed.The characteristics of Zn diffusion in InP/InGaAs(P)heterostrueturematerials at comparatively low temperature have been studied,and it has been found for the first time that Zndiffusion rate is proportional to the square of phosphorus content of the InGaAsP materials.     

Electronic characterization of heterojunctions by surface potential monitoring

An original approach for studying the formation of semiconductor heterojunctions and their electronic properties is discussed and illustrated. Monitoring the changes in the surface potential during the heterojunction formation lends itself to direct measurement of the band discontinuities, Debye length, and the width of the space-charge region at heterojunction interfaces. The contribution of an interface dipole is considered. The technique is demonstrated by a technologically significant experimental example.     

Effects of deposition rate on the size of self-assembled InP islands formed on GaInP/GaAs(100) surfaces

Utilizing the Stranski-Krastanov growth mode, three-dimensional InP islands are formed on a GalnP/GaAs surface using metalorganic chemical vapor deposition. The islands have been investigated with atomic force microscopy, and the effect of the deposition rate on the shape of the islands has been quantified. The height of the islands varies with deposition rate, whereas the basediameters are nearly constant around 1260 ± 35Å. The island height is 290 ± 12 Å at a high (2.6 ML/s) deposition rate and decreases to approximately 250 ± 16 Å for low (0.1 ML/ s) and moderate (0.8 ML/s) deposition rates.     

Use of tertiarybutylphosphine for the growth of InP and GaAs1-xPx

A newly-developed phosphorus source, tertiarybutylphosphine (TBP), which is much less toxic than PH₃, has been used to grow InP and GaAs_1-xP_x by atmospheric pressure organometallic vapor phase epitaxy (OMVPE). Excellent morphologies are obtained for the growth of InP between 560 and 630° C for TBP partial pressures larger than 0.5 x 10^-3. For the first time, V/III ratios as low as 3 have been used to grow InP epilayers with featureless morphologies at 600° C. To obtain good morphologies at both lower and higher temperatures, higher TBP partial pressures are necessary. The electron mobility increases and the electron density decreases as the temperature is increased. The highest room temperature mobilities and lowest electron densities, obtained at 630° C, are 3800 cm²/V-sec and 3 x 10¹⁵ cm^-3, respectively. The 10 K photoluminescence spectra of the InP epilayers at higher growth temperatures show no carbon contamination. Bound excition half widths as low as 3.0 meV have been measured. The use of TBP to replace PH₃ in the growth of GaAs_1-xP_x results in a nearly linear relationship between vapor and solid composition at 610° C,i.e., the P distribution coefficient is nearly unity. This contrasts sharply with the very low P distribution coefficient obtained using PH₃ at such low growth temperatures.     

On the role of interface properties in the degradation of metalorganic vapor phase epitaxially grown Fe profiles in InP

Fe doping profiles in InP layers grown by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) were investigated by secondary ion mass spectroscopy. Different pre-treatments of the InP substrates proved to have substantially different effects on the Fe profiles which strongly indicate the relevance of underlying interfaces to dopant diffusion in subsequent layers, at least in the case of dopants occupying the group-III sublattice. We attribute the degradation of Fe profiles observed for some kinds of treatment to the emission of In interstitials from surfaces covered by oxides or other residues which are incompletely removed during the MOVPE preheat cycle. A favorable substrate preparation method for avoiding Fe profile degradation relies on etching by 5:1:1 H₂SO₄:H₂O₂:H₂O at room temperature followed by 30 min deionized water rinsing.