A. T. Macrander

Misfit stress in InGaAs/InP heteroepitaxial structures grown by vapor‐phase epitaxy

Misfit stress in InGaAs/InP heteroepitaxial structures grown by hydride‐transport vapor phase epitaxy has been studied using an x‐ray technique to measure the wafer curvature and using an x‐ray double crystal diffractometer to measure mismatches. The stress calculated from the measured radius of curvature was, in all cases, found to be smaller than the value predicted from the lattice mismatch using the simple beam theory and assuming a coherent interface. A simple argument is used to show that the parallel mismatch is directly related to the density of misfit dislocations. By taking into account both the presence of misfit dislocations and tetragonal distortion, relationships between the curvature, density of interfacial misfit dislocations, relaxed lattice mismatch, and measured tetragonally distorted vertical and parallel mismatches are derived. Predicted values for the radius of curvature agree very well with measured values. The results also indicate that in the presence of interfacial misfit disloca...

Electrical characterization of Fe‐doped semi‐insulating InP grown by metalorganic chemical vapor deposition

The bulk resistivity of Fe‐doped metalorganic chemical vapor deposited grown epitaxial InP was determined from current‐voltage and capacitance measurements made on Schottky‐diode‐like devices. The current‐voltage data exhibit both an ohmic and a space‐charge‐limited regime, and the capacitance was found to be independent of applied bias. The electrical thickness was obtained from the capacitance using a relationship appropriate for current injection. Data for two samples representing both thin (∼1 μm) and thick (∼9 μm) epitaxial layers are presented. The resistivities were 6.5×107 Ω cm and 2.2×108 Ω cm.

Lattice‐mismatch‐generated dislocation structures and their confinement using superlattices in heteroepitaxial GaAs/InP and InP/GaAs grown by chemical beam epitaxy

We report a detailed transmission electron microscopy and x‐ray double‐crystal diffractometry study of the lattice‐mismatch‐induced defect structures in InP grown on (100) GaAs substrate and vice versa by chemical beam epitaxy. A rough estimate of the dislocation densities in GaAs on InP is 2×1010 cm−2 at the interface and 5×107 cm−2 at the surface of the epilayer. The corresponding values in InP on GaAs are slightly lower as expected for the compressive stress state for InP. The majority of the dislocations lie on the {111} slip planes with 1/2 [110]‐ and 1/2 [101]‐type Burgers vectors. A cross‐grid‐type interfacial misfit dislocation array is not observed. Instead, a complicated dislocation structure near the interface, consisting of overlapping pyramidal dislocation tangles (PDT) similar to those observed previously in InGaAs on InP caused by interfacial misfit particles, is presented. The interfacial dislocations form a cellular structure in GaAs on InP and a random structure in InP on GaAs. A Moire f...

GaAs‐on‐Si: Improved growth conditions, properties of undoped GaAs, high mobility, and fabrication of high‐performance AlGaAs/GaAs selectively doped heterostructure transistors and ring oscillators

Improved growth conditions by molecular‐beam epitaxy (MBE) and fabrication of state‐of‐the‐art AlGaAs/GaAs selectively doped heterostructure transistors (SDHTs) and ring oscillators on Si substrates are reported. In MBE growth, use of minimum As4:Ga flux ratio during initial nucleation combined with in situ thermal cycles gave a marked improvement in material quality. With this method, FWHM of x‐ray rocking curves was measured as low as 135 arcsec for a 3.5‐μm‐thick GaAs layer on Si. Although 3‐μm‐thick undoped GaAs buffer layers on p‐type Si substrates were fully depleted under a Schottky contact, a parallel n‐type conduction path confined in a thin region (<0.1 μm) near the GaAs/Si interface was sometimes observed whose sheet density (1012–1013 cm−2) and mobility (600–900 cm2 V−1 s−1) were independent of temperature between 300 and 77 K. This parallel conduction was successfully prevented by doping 0.1 μm GaAs with 5–10×1016 cm−3 Be atoms near the interface. In AlGaAs/GaAs selectively doped heterostruct...

X‐ray double‐crystal characterization of highly perfect InGaAs/InP grown by vapor‐phase epitaxy

Rocking curves of a 0.78‐μm layer grown on a 3.35° off‐(100) substrate by the hydride process have been compared to detailed calculations using x‐ray dynamical diffraction theory. The observed linewidth and peak convoluted reflecting power of the (400) reflection are 32 arc s and 12.4% as compared to calculated values of 26.6 arc s and 17.4%. We used a symmetric (100) InP first crystal, and the calculations were made for this exact geometry. Anomalous dispersion was not neglected. We report the observation of Bragg geometry Pendellosung fringes for this InGaAs layer. As many as six fringes having a separation of 26 arc s were found to be clearly visible. This spacing was fit to obtain the layer thickness. We conclude that, so far as we are aware, our material is the best, as judged from an x‐ray point of view, ever reported for the vapor‐phase epitaxy process.

X‐ray and Raman characterization of AlSb/GaSb strained layer superlattices and quasiperiodic Fibonacci lattices

Double‐crystal rocking curves of samples grown on (001)‐oriented GaSb substrates by molecular‐beam epitaxy have been analyzed by fitting computer simulations to data for the symmetric (004) and (002) reflections and for asymmetric (115) reflections. Rocking curves revealed a multiplicity of superlattice diffraction peaks. Dynamical diffraction theory using Abeles matrix method [D. W. Berreman, Phys. Rev. B 14, 4313 (1976)] was applied for the symmetrical reflections. We compare our results to standard kinematical simulations, and we find that there are significant differences. For the asymmetric reflections a new dynamical computer simulation code [D. W. Berreman and A. T. Macrander, Phys. Rev. B 37, 6030 (1988)] involving an 8×8 matrix solution of Maxwell’s equations was used. Lattice incoherency was determined from measurements of the in‐plane mismatch. Dramatic diffraction peak broadening was observed for incoherent superlattices, and this broadening was attributed to a mosaic structure formed by misfi...

High resistivity in InP by helium bombardment

Helium implants over a fluence range from 1011 to 1016 ions/cm2, reproducibly form high resistivity regions in both p‐ and n‐type InP. Average resistivities of greater than 109 Ω cm for p‐type InP and of 103 Ω cm for n‐type InP are reported. Results are presented of a Monte Carlo simulation of helium bombardment into the compound target InP that yields the mean projected range and the range straggling.

Recombination enhanced defect annealing in n‐InP

The first example of a recombination enhanced defect reaction in InP is reported. The major defect E(0.79 eV) introduced by 1‐MeV electron irradiation of p+n junctions, formed by Zn‐doped epilayers on undoped n‐type substrates, is not observed with Schottky barrier structures on similar material. The defect exhibits a reduction in activation energy of recovery from 1.3 eV under pure thermal annealing to 0.42 eV with minority‐carrier (hole) injection. The enhanced reaction rate is proportional to the square of the injected current showing that the process results from two particle capture.

X-ray diffraction from corrugated crystalline surfaces and interfaces

Satellite peaks analogous to superlattice peaks have been observed for both corrugated InP substrates and for such substrates overgrown with epitaxial InGaAsP. These satellites are entirely due to the corrugations. High-resolution x-ray diffraction using extremely asymmetric reflections in the glancing exit configuration was used. A kinematical expression for the intensities of the satellite peaks is derived for strain-free structures.

Characterization of InP/GaAs/Si structures grown by atmospheric pressure metalorganic chemical vapor deposition

The thickness dependence of material quality of InP‐GaAs‐Si structures grown by atmospheric pressure metalorganic chemical vapor deposition was investigated. The InP thickness was varied from 1–4 μm, and that of the GaAs from 0.1–4 μm. For a given thickness of InP, its ion channeling yield and x‐ray peak width were essentially independent of the GaAs layer thickness. The InP x‐ray peak widths were typically 400–440 arcsec for 4‐μm‐thick layers grown on GaAs. The GaAs x‐ray widths in turn varied from 320–1000 arcsec for layer thicknesses from 0.1–4 μm. Cross‐sectional transmission electron microscopy showed high defect densities at both the InP‐GaAs and GaAs‐Si interfaces. In 4‐μm‐thick InP layers the average threading dislocation density was in the range (3–8)×108 cm−2 with a stacking fault density within the range (0.4–2)×108 cm2. The He+ ion channeling yield near the InP surface was similar to that of bulk InP (χmin∼4%), but rose rapidly toward the InP‐GaAs heterointerface where it was typically around ...