W. J. Moore

Surface reconstruction phase diagrams for InAs, AlSb, and GaSb

Abstract : We present experimental flux-temperature phase diagrams for surface reconstruction transitions on the 6.1As compound semiconductors. The phase transitions occur within or near typical substrate temperature ranges for growth of these materials by molecular beam epitaxy and therefore provide a convenient temperature standard for optimizing growth conditions. Phase boundaries for InAs (0 0 1) [(2*4)->(4*2)], AlSb (0 0 1) [c(4*4)->(1*3)], and GaSb (0 0 1) [(2*5)_>(1*3)] are presented as a function of substrate temperature and Group V-limited growth rate (proportional to flux), for both cracked and uncracked Group V species. We discuss differences between materials in the slopes and offsets of the phase boundaries for both types of Group V species.

Infrared dielectric constant of gallium arsenide

The real dielectric constant of gallium arsenide has been determined at 300 and at 5 K from fits to observed interference in transmission of thin samples with parallel surfaces. Measurement was carried out over all or part of the range 30–4000 cm−1. An accuracy of ±0.5% is estimated based on the quality of the analytic fits and the sample thickness measurement technique. We find at 300 K, e0=12.90 and e∞=10.86. At 5 K, e0=12.46 and e∞=10.58. An analytic expression for the dielectric function is given which allows accurate values of the real dielectric constant to be determined throughout most of the 0–4000 cm−1 spectral range. The observed ratio e0/e∞ agrees with the Lyddane–Sachs–Teller relation calculated with Raman values of transverse and longitudinal optical phonon frequencies to better than 0.1% at 300 and at 5 K.

Optimum growth parameters for type-II infrared lasers

The surface, structural, and optical properties of InAs/InGaSb/AlSb mid-infrared lasers grown by molecular beam epitaxy have been systematically studied, respectively, by Nomarski differential interference contrast, high-resolution x-ray diffraction, and variable-temperature photoluminescence. It is found that the optimum growth temperature is between 400 and 450 °C, based on the calibrated transmission thermometry. In addition, the impact of interfacial bond type and Sb sources has been investigated. A 5.91 μm laser, grown with the optimal growth parameters, exhibits a maximum cw operating temperature of 210 K.

Infrared dielectric function of wurtzite aluminum nitride

The infrared dielectric function of wurtzite AlN has been determined by fitting an analytic Lorentzian dielectric function to experimentally observed interference fringes in infrared transmission. The analytic model is scaled to agree with recent measurements of the visible refractive index, and the experiment and model extend to the submillimeter range of the infrared. A complete, experimentally verified dielectric function is found from the visible to the submillimeter spectral region for radiation with E⊥c axis, and an analytic model is produced for E‖c axis. Refractive indices and extinction coefficients from the visible to zero frequency are presented.

Photoluminescence and infrared spectroscopy of acceptors in GaAs

Time‐resolved and continuous wave (cw) photoluminescence studies and infrared absorption spectroscopy have been carried out on bulk liquid‐encapsulated Czochralski crystals of GaAs grown from Ga‐rich and stoichiometric melts. These samples all exhibited the 78‐meV residual acceptor which has been attributed previously to the neutral state of the GaAs antisite double‐acceptor defect. The temperature dependence and time‐resolved studies of the ∼1.44‐eV photoluminescence band associated with the 78‐meV residual acceptor in these samples demonstrates conclusively that the luminescence bands reported by various workers in the 1.441–1.443 eV range are all attributable to a donor‐acceptor pair transition involving the same acceptor level. Two distinctly different photoluminescence bands at 1.283 eV (236‐meV level) and 1.316 eV (203‐meV level) can be distinguished on the basis of peak energies, temperature dependence, and time decay characteristics. The difference between these two bands was not recognized previo...

Infrared Photoconductive Characteristics of Boron‐Doped Germanium

Boron‐doped germanium having very low levels of compensation is shown to be useful for detection of far infrared radiation in the 50–125 μ range. The results of measurements of time constant, dc characteristics, photoresponse, and spectral response of several Ge(B) detectors is presented and discussed. Detectors having a peak detectivity of 2.1×1011 cm‐cps½‐W−1 at 108 μ and a low dynamic impedance have been achieved. The cross section for the capture of a free hole by an ionized boron impurity in germanium at 4.2°K, about 4×10–11cm2, is significantly larger than the corresponding cross section for n‐type impurities in germanium.

Determination of temperature dependence of GaSb absorption edge and its application for transmission thermometry

Transmission spectra of GaSb have been obtained over a temperature range from 10 to 470 °C. Using this information, transmission thermometry is applied to obtain accurate measurements of sample temperature during molecular beam epitaxy growth on GaSb substrates. A GaSb surface reconstruction transition is determined as a function of Sb flux and substrate temperature, establishing a laboratory-independent temperature standard.

Transport properties of Be- and Si-doped AlSb

Thick epitaxial layers of AlSb(Si) and AlSb(Be) were grown by molecular beam epitaxy and characterized by variable-temperature Hall/van der Pauw measurements. Si is shown to be predominantly an acceptor in AlSb, with an energy level 33±4 meV above the top of the valence band. Be is also an acceptor, with an energy level 38±4 meV above the top of the valence band. Be is a robust doping source for p-AlSb for carrier densities ranging from 1015 to 1019 cm−3. Background impurity levels in AlSb can be assessed by measuring the transport properties of lightly doped AlSb(Be) layers.

Photoluminescence of InAs1−xSbx/AlSb single quantum wells: Transition from type-II to type-I band alignment

Infrared photoluminescence has been used to study the band-gap energy of InAs1−xSbx digital superlattices and band alignment of InAs1−xSbx/AlSb quantum wells at 5 K. It is found that the InAs1−xSbx digital alloys have a smaller effective band gap than InAs1−xSbx random alloys. In addition, the valence band offset between type-II InAs/AlSb is determined to be 130 meV. This number reduces as the Sb mole fraction in InAs1−xSbx is increased, and the alignment between InAs1−xSbx/AlSb becomes type I when x>0.15.

INFRARED DIELECTRIC CONSTANT OF CUBIC SIC

The real dielectric constant for chemical vapor deposition 3C‐SiC grown on silicon (Si) has been determined at 300 K and at 5 K from an analytic fit to interference fringes in transmission over the spectral range from the near infrared to the submillimeter region. This technique is capable of high accuracy being limited typically by the sample thickness and accuracy with which the thickness is measured. The resulting real dielectric constant is lower than the values usually attributed to this material. We find: at 300 K e 0=9.52 and e ∞=6.38; at 5 K e0=9.28 and e ∞=6.22. In all cases the estimated error is ±0.8%. The observed ratio e0 /e∞ agrees with the Lyddane–Sachs–Teller relation to 0.1% at 300 K and 0.2% at 5 K.