Growth and characterization of Ga1−xInxAs by low pressure metalorganic chemical vapor deposition

Conditions for growth at 550°C of high structural quality GaInAs by LPMOCVD are presented. The sensitivity of compositional grading to changes in the V/III molar ratio, growth rate and inclusion of InP buffer layers is discussed. Crystalline uniformity is indicated by double crystal x-ray rocking curves with FWHM (GaInAs) = 0.017°. By careful control of the V/III molar ratio, epitaxial GaInAs/InP heterostructures with δa/a ≤ 10⁻⁴ can be grown. Quantitative data for the TEIn-AsH₃ elimination reaction rate is presented. The composition of Ga_1−xIn_xAs which is expected in the presence of this reaction is calculated; evaluation of the corresponding rate constant shows that the adduct formation reaction proceeds at a modest but detectable rate. The problems associated with the purity of electronic grade triethylindium (TEIn) are addressed. Impurities in commercial TEIn have been determined by low resolution mass spectroscopy.     

Metalorganic InP and Inx Ga1-x,Asy P1-y,on InP epitaxy at atmospheric pressure

We present a procedure for the MOVPE of InP as simple as the one currently used for GaAs. InP and InGaAsP alloys are grown on InP substrates using trimethy1indium (TMI), phosphine, trimethylgallium (TMG) and arsine. The choice of carrier gas is important ; a mixture of hydrogen and nitrogen allowed us to grow uniform layers over large areas at atmospheric pressure, without pyrolizing the phosphine or separating the input reactants. Preliminary characterization results are presented. Most information contained in this paper was presented at the 1983 Electron Materials Conference as paper Cl.     

Controlled oxygen incorporation in indium gallium arsenide and indium phosphide grown by metalorganic vapor phase epitaxy

The defect engineering in metalorganic vapor phase epitaxy In_xGa_1-xAs and InP by controlled oxygen doping using diethyl aluminum ethoxide (DEALO) was developed in this study. DEALO doping has led to the incorporation of Al and O, and the compensation of shallow Si donors in In_xGa_1−xAs: Si with 0 ≤ x ≤ 0.25. With the same DEALO mole fraction during growth, the incorporation of Al and O was found to be independent of x, but the compensation of Si donors decreases with increasing In content. Deep level transient spectroscopy analysis on a series of In_xGa_1-xAs: Si. samples with 0 ≤ x ≤ 0.18 revealed that oxygen incorporation led to a set of deep levels, similar to those found in DEALO doped GaAs. As the In composition was increased, one or more of these deep levels became resonant with the conduction band and led to a high electron concentration in oxygen doped In_0.53Ga_0.47As. Low temperature photoluminescence emission measurements at 12K on the same set of samples revealed the quenching of the near-band edge peak, and the appearance of new oxygen-induced emission features. DEALO doping in InP has also led to the incorporation of Al and O, and the compensation of Si donors due to oxygen-induced multiple deep levels.     

The effect of trimethylaluminum concentration on the incorporation of P In AlxGa1−xPyAs1−y grown by organometallic vapor phase epitaxy

The organometallic vapor phase epitaxial (OM-VPE) growth of Al_xGa_1-xP_yAs_1-y on graded GaP_yAs_1-yGaAs in the compositional range 0 < x < 0.9 and 0 < y < 0.6 is reported. It is found that composition control can be easily achieved, and that the vapor phase ratio of trimethylaluminum to trimethylgallium strongly influences the incorporation of P in the solid. A model is developed which explains this in terms of competing reaction rates. The model gives a good fit to the experimental data.     

Ga1-xinxas - inp abrupt heterostructures grown by MOVPE at atmospheric pressure

High quality InP and Ga_1-x In_xAs layers have been grown on InP substrates using MOVPE growth at atmospheric pressure. Excellent material quality has been obtained using triethylindium and trimethylgallium sources(n = 1.7 10¹⁴ cm^-3, μ = 106 000 cm²V^-1s^-1 at 77 K for InP andn = 1 ? 3 10¹⁵ cm^-3, μ= 75 000 cm²V^-1 s^-1 at 77 K for Ga_1-xIn_xAs). The InP/Ga_1-xIn_xAs interface width obtained is very small (10 Å). The first PIN diodes grown by the process exhibit excellent characteristics.     

基于InP衬底的晶格失配In0.68Ga0.32As的MOCVD生长及其特性研究

采用MOCVD生长技术在InP衬底上成功实现了晶格失配的3μm In0.68 Ga0.32As薄膜生长.通过As组分的改变,利用张应变和压应变交替补偿的InAsxP1-x应变缓冲层结构来释放由于晶格失配所产生的应力,在InP衬底上得到了与In0.68Ga0.32 As晶格匹配的InAsxP1-x“虚拟”衬底,通过对缓冲层厚度的优化,使应力能够在“虚拟”衬底上完全豫弛.通过原子力显微镜(AFM)、高分辨XRD、透射电镜(TEM)和光致发光(PL)等测试分析表明,这种释放应力的方法能够有效提高In0.68 Ga0.32 As外延层的晶体质量.     

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.     

Efficient 2.0–2.6 μm wavelength photoluminescence from narrow bandgap InAsP/InGaAs double heterostructures grown on InP substrates

Photoluminescence spectra and efficiency have been measured for several strained InAs_yP_1−yIn_xGa_1−xAs (0.28 < y ≤ 0.62; 0.66 ≤ x ≤ 0.83) double heterostructures grown by vapor phase epitaxy on InP substrates with graded InAsP buffer layers. Luminescence peak positions between the wavelengths of 1.99 and 2.57 (μm at a temperature of 295K are consistent with bandgap luminescence from the In_xGa_1−xAs active regions. Despite a high density of dislocations in the buffer layers, internal radiative recombination efficiencies of from 25 to 50% for the structures are found at 295K.     

Electrical properties of InAlAs/InAsxP1-x/InP composite-channel modulation-doped structures grown by solid source molecular beam epitaxy

We report on the electrical characteristics of the two-dimensional electron gas (2DEG) formed in an InAlAs/InAs_xP_1-x/InP pseudomorphic composite-channel modulation-doped (MD) structure grown by solid source (arsenic and phosphorus) molecular beam epitaxy (SSMBE). The As composition, x, of strained InAs_xP_1-x was determined by x-ray diffraction analysis of InP/InAs_xP_1-x/InP multi-quantum wells (MQWs) with compositions of x=0.14 to x=0.72. As the As composition increases, the room temperature sheet resistance of InAlAs/InAs_xP_1-x/InP composite-channel MD structures grown over a range of As compositions decreased from 510 to 250 Ω/cm², resulting from the greater 2DEG confinement and lower electron effective mass in the InAs_xP_1-x channel as x increases. The influence of growth conditions and epitaxial layer designs on the 2DEG mobility and concentration were investigated using 300 K and 77 K Hall measurements. As the exposure time of the As₄ flux on the growth front of InAs_xP_1-x increased during growth interruptions, the 2DEG mobility, in particular the 77K mobility, was considerably degraded due to increased roughness at the InAlAs/InAs_xP_1-x interface. For the InAlAs/InAs_0.6P_0.4/InP composite-channel MD structure with a spacer thickness of 8 nm, the room temperature 2DEG mobility and density were 7200 cm²/Vs and 2.5 × 10¹² cm⁻², respectively. These results show the great potential of the InAlAs/InAs_xP_1-x/InP pseudomorphic composite-channel MD heterostructure for high frequency, power device applications.     

Properties of Zn-doped P-type In0.53Ga0.47as grown by vapor phase epitaxy (VPE) on InP substrates

Electrical properties of Zn-doped, p-type In_0.53Ga_0.47As grown by the vapor phase epitaxy (VPE) technique are presented. High (p ∼ 4.0 × 10¹⁹ cm⁻³) p-type doping and low resistivity (ρ ∼ 2.8 × 10⁻³ Ωsu−cm) was obtained. These propertie's are useful in the formation of ohmic contacts in laser diodes and photodiodes fabricated from the quaternary and ternary alloy systems. A calibration curve for the non-destructive determination of carrier concentration from photoluminescence linewidths has been obtained.     

Measured compositions and laser emission wavelengths of GaXIn1−XAsyP1−y lpe layers lattice-matched TO InP Substrates

The alloy compositions of Ga_XIn_1−XAs_yP_1−y LPE layers lattice-matched to InP substrates have been determined by electron microprobe analysis. The composition data are well repre-sented by x = 0.40y + 0.067y². The emission wavelengths of lattice-matched Ga_XIn_1−XAs_yP_1−y/InP double-heterostructure diode lasers have been measured at 300 and 80 K. The photon energies for laser emission at 300 K are given by hΝ(eV) = 1.307 − 0. 60y + 0.03y². The emission energies at 80 K are 57 meV higher. This work was sponsored by the Department of the Air Force.     

The preparation of modulation-doped GaAs/GaAs1-xPx strained-layer superlattices by metal organic chemical vapor deposition

Modulation-doped and uniformly doped GaAs/GaAs_1-xP_x strained-layer superlattices (SLS’s) have been prepared by metal organic chemical vapor deposition in a vertical, atmospheric pressure, quartz reaction chamber. The layers were doped with Se or Si by using a H₂Se or SiH₄ source and by using a vent-run valve-configuration to minimize dopant tailing. Carrier concentrations and mobilities were determined from Hall measurements at 300 and 77 K. The Se modulation-doped SLS’s with carrier concentrations in the range of 10¹⁶ to 10¹⁸ cm^-13 exhibited enhanced transport properties when compared to the properties of epitaxial GaAs prepared under the same conditions. The use of molecular sieves to purify the arsine or the use of SiH₄ resulted in lower mobilities for the SLS’s and the epitaxial GaAs layers. The presence of surface cracking or a large residual strain in the SLS’s also caused the modulation-doped SLS’s to have lower mobilities.     

Calculation of energy band gaps in quaternary iii/v alloys

The dielectric theory of electronegativity is applied to the calculation of the compositional dependence of the energy band gap for quaternary III/V alloys of type A_l-xB_xC_1-yD_y and A_1-x-yB_xC_yD. The departure from linearity of E_G versus x and y is taken to be the sum of two terms, the intrinsic or virtual crystal term and the extrinsic term due to effects of aperiodicity which for one type of alloy may occur on both sublattices. Rather than simply treating the quaternary as an average of the bounding ternary systems, as has been common in the past, the intrinsic departure from linearity is calculated by assuming E_h,i,C, and D_av to vary linearly with x and y. The result is a smaller intrinsic deviation from linearity and a much better fit to existing data in the system Ga_1-xIn_xAs_1-y P_y. The calculation is also applied to three systems where no data exist but which are of great interest because of their potential application for the fabrication of lattice matched tandem solar cells: Ga_l-xA1_xAs_l-ySb_y. Ga_1-x-yA1_xIn_yAs, and GaAs_1-x-yP_xSb_y.     

OMVPE growth of InP and Ga0.47ln0.53as using ethyldimethylindium

We report the organometallic vapor phase epitaxial (OMVPE) growth of InP and Ga_0.47In_0.53As using a new organometallic indium source, ethyldimethylindium (EDMIn), rather than the traditional sources triethylindium (TEIn) or trimethylindium (TMIn). EDMIn is a liquid at room temperature and its vapor pressure at 17° C was found to be 0.85 Torr using thermal decomposition experiments. The growth results using EDMIn were compared to those using TMIn in the same atmospheric pressure reactor. For InP, use of EDMIn resulted in a high growth efficiency of 1.3 × 10⁴ μm/ mole, which was independent of the growth temperature and comparable to the growth efficiency obtained with TMIn. The high growth efficiency is consistent with the observation of no visible parasitic gas phase reactions upstream of the substrate. The 4K photoluminescence (PL) spectra consist of a peak due to bound excitons and an impurity related peak 38 meV lower in energy. This impurity peak is ascribed to conduction band to acceptor transitions from carbon, due to the decreasing relative intensity of this peak with increasing V/III ratio. The relative intensity of the C impurity peak decreases by five times when the growth temperature is increased from 575 to 675° C, with a corresponding increase in the room temperature electron mobility from 725 to 3875 cm²/ Vs. For GalnAs lattice-matched to InP, use of EDMIn also resulted in a temperatureindependent high growth efficiency of 1.0 x 10⁴ μm/mole, indicating negligible parasitic reactions with AsH₃. The In distribution coefficient was nearly constant at a value of 0.9, however the run to run composition variation was slightly higher for EDMIn than for TMIn. The 4K PL showed donor-acceptor pair transitions due to C and Zn. The C impurity peak intensity decreased dramatically with increasing growth temperature, accompanied by an increase in the room temperature electron mobility to 5200 cm²/Vs. Overall, the growth of both InP and GalnAs using EDMIn was qualitatively similar to that using TMIn, although the room temperature electron mobilities were lower for the new source than for our highest purity bottle of TMIn.     

Liquid phase epitaxial growth and characterization of high purity lattice matched GaxIn1-xAs ON <111>B InP

High purity Ga_xIn_1-x As has been grown lattice matched on <111>B InP by liquid phase epitaxy. Silicon, the residual impurity, is purged from the melt by long time baking in a hydrogen atmosphere with slight ambient water vapor concentration. Epitaxial layers with a net electron concentration as low as 3.5 × 10¹⁴ cm^-3 and a liquid nitrogen mobility of 70,000 cm²/Vsec have been grown. The room temperature mobility is shown to be significantly higher than GaAs over a wide range of net electron concentrations useful for device applications, with the highest value of μ₃₀₀ = 13,800 cm²/Vsec on a sample with n = 1.9 × I0¹⁵ cm_-3     

Horizontal unseeded vapor growth of Iv-Vi compounds and alloys

Large, high-quality crystals of various Pb-salt compounds and alloys have been grown from the vapor by a horizontal, unseeded, closed-tube method. The optimum growth conditions have been experimentally determined. The crystalline imperfections and electrical properties of the crystals were examined. In a series of growth experiments on PbTe, the source materials were prepared by adding small quantities of Pb to much larger quantities of zone-melted PbTe. This method makes it possible to control the source and as-grown crystal compositions for excess Pb or Te concentrations in the 10¹⁸/cm³ range. From the results of these experiments it was found that the composition of zone-melted PbTe (i. e., the maximum-melting point composition of PbTe) corresponds to a hole concentration of approximately 1 x l0¹⁹/cm³. This work was sponsored by the Department of the Air Force.     

Systematic optical and x-ray study of In x Ga1−x As on InP

We present a systematic study of In _x Ga_1−x As on InP grown by molecular beam epitaxy using the characterization techniques of Fourier transform photoluminescence, x-ray diffraction, micro-Raman spectroscopy, and photoreflectance spectroscopy. The four techniques were used to determine and correlate the fundamental parameters of band-gap energy, phonon frequency and composition. Comparing room temperature (293 K) PL and low temperature PL indicate the presence of a partially ionized acceptor with binding energy of about 13 meV in the unintentionally doped material. Double crystal x-ray diffraction (XRD) using a symmetric <400> and asymmetric <224> reflections was also employed. The use of two reflections gives precise lattice constants, composition, and extent of film relaxation. Micro-Raman spectroscopy was used to measure phonon frequencies in the In _x Ga_1−x As films and correlated to XRD composition. Room temperature photoreflectance (PR) was used to determine band-gap energy for both the low and intermediate field cases. Band gap energies determined at room temperature by PL and PR were in agreement within experimental error.     

Alkoxide precursors for controlled oxygen incorporation during metalorganic vapor phase epitaxy GaAs and AlxGa1−xAs growth

Controlled oxygen incorporation in GaAs using Al-0 bonding based precursors, dimethyl aluminum methoxide (DMALO) and diethyl aluminum ethoxide (DEALO), is presented in this investigation. A comparison study of oxygen incorporation kinetics between nominally undoped Al_xGa_1−xAs using trimethyl aluminum and DMALO-doped GaAs suggests that DMALO is one of the most important oxygen-bearing agents responsible for unintentional oxygen incorporation in Al_xGa_1−xAs. Controlled oxygen doping using DEALO is reported for the first time. Oxygen incorporation behavior, especially on the effect of the V/III ratio, was found to be quite different from the case of DMALO, mainly due to the differences between methyl- and ethyl-based growth chemistries. Physical, electrical, and optical properties of these oxygen-doped GaAs are also reported.     

Improved selective growth of InP around dry-etched mesas by metalorganic chemical vapor deposition at low growth temperature

A comparative study has been carried out regarding selective embedding growth of InP by metalorganic chemical vapor deposition (MOCVD) around dry-etched mesas, using two types of reactors: a conventional horizontal type and a highspeed rotating-susceptor type. In the case of the conventional horizontal-type MOCVD, overgrowth on the mask was observed when the growth temperature was low (600°C). On the other hand, an almost planar grown surface without such overgrowth was achieved by using the high-speed rotating-susceptor MOCVD for a wide range of growth temperatures, especially even at a low growth temperature of 580°C. Regarding the high-speed rotating-susceptor MOCVD, we have also investigated the effects of dopants on the growth behaviors and have found a remarkable difference between n-type S-doped and p-type Zn-doped InP in the growth behaviors. The mechanism for suppressing overgrowth in case of the high-speed rotating-susceptor MOCVD, as well as the cause for the different effects between the dopants, are discussed.     

Group-V composition control for InGaAsP grown by gas source molecular beam epitaxy

Based on our kinetics models for gas source molecular beam epitaxy of mixed group-V ternary materials, the group-V composition control in In_yGa_1−yAs_1−xP_x epilayers has been studied. The P or As composition in In_yGa_1−yAs_1−xP_x (lattice matched to InP or GaAs) can be obtained from a simple equation for substrate temperatures below 500°C. This has been verified by a series of experimental results.