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Quantum wells of InGaAs clad by InAlAs were grown on AlGaAsSb buffer layers by molecular beam epitaxy. The buffer layer lattice parameters were near 6.0 , yielding tensile strains up to 2% in the InGaAs and InAlAs. Room-temperature electron mobilities of 9000-11,000 cm2/V s were achieved. Field-effect transistors (FETs) were fabricated and exhibited good DC and RF characteristics. Previous work demonstrated compressively-strained GaSb quantum wells on similar buffer layers with high hole mobilities and good transistor performance. Hence, a single buffer layer of AlGaAsSb should be suitable for complementary circuits comprised of n-channel FETs based on the mature InGaAs/InAlAs technology and p-channel FETs based on high-mobility antimonides., Published in the Journal of Crystal Growth, v388 p92 97, 2014.

In this report, we study the effectiveness of hydrogen plasma surface treatments for improving the electrical properties of GaSb/Al2O3 interfaces. Prior to atomic layer deposition of an Al2O3 dielectric, p-GaSb surfaces were exposed to hydrogen plasmas in situ, with varying plasma powers, exposure times, and substrate temperatures. Good electrical interfaces, as indicated by capacitance-voltage measurements, were obtained using higher plasma powers, longer exposure times, and increasing substrate temperatures up to 250 deg C. X-ray photoelectron spectroscopy reveals that the most effective treatments result in decreased SbOx, decreased Sb, and increased GaOx content at the interface. This in situ hydrogen plasma surface preparation improves the semiconductor/insulator electrical interface without the use of wet chemical pretreatments and is a promising approach for enhancing the performance of Sb-based devices., Published in Applied Physics Letters, v101 article ID 231601, 3 Dec 2012.

Sb-based pN heterojunction diodes at 6.2 Angstroms consisting of narrow bandgap p-type In0.27Ga0.73Sb and wide bandgap n-type In0.69Al0.41As0.41Sb0.59, have been fabricated and measured. These diodes show excellent electrical characteristics with an ideality factor of 1.2 and high current density. S-parameter measurements and subsequent analysis show that these diodes have RC-cutoff frequencies over 1 THz, making these diodes excellent choices for high-frequency applications, such as sub-harmonic mixers for frequency conversion.

Heterostructures consisting of an InGaSb quantum well situated between AlGaSb barriers were grown by molecular beam epitaxy. Calculations indicate a type-I band structure with substantial valence and conduction band offsets that can allow for the confinement of either electrons or holes in the InGaSb. Quantum wells with n-type conduction were achieved using modulation doping, with Te located in the barrier above the quantum well. A set of barrier layers was found which resulted in a sample with an In0.2Ga0.8Sb quantum well that exhibited an electron mobility of 3900cm2/V s as grown. After removal of upper barrier layers including the Te by selective etching, the conductivity switched to p-type, with hole mobilities near 800cm2/V s. This design could allow the integration of low-power n- and p-channel field-effect transistors for complementary logic applications., Published in Journal of Crystal Growth, v312 p37-40, 2009.

InAs-based heterostructure barrier varactor (HBV) diodes with In0.3Al0.7As0.4Sb0.6 as the barrier material are demonstrated. Current-voltage and capacitance-voltage characteristics, as well as S-parameters, of HBV diodes with varying barrier thicknesses are examined. Maximum capacitance values and maximum- to-minimum capacitance ratios greater than those predicted by traditional HBV models were measured. The HBVs' unconventional behavior in terms of charge accumulation layers adjacent to the wide bandgap barrier is discussed., Published in Solid-State Electronics v52 p1829-1832, 2008.

InAs-based heterostructure barrier varactor (HBV) diodes with In0.3Al0.7As0.4Sb0.6 as the barrier material are demonstrated. Current-voltage and capacitance-voltage characteristics, as well as S-parameters, of HBV diodes with varying barrier thicknesses are examined. Maximum capacitance values and maximum- to-minimum capacitance ratios greater than those predicted by traditional HBV models were measured. The HBVs' unconventional behavior in terms of charge accumulation layers adjacent to the wide bandgap barrier is discussed., Published in Solid-State Electronics v52 p1829 1832, 2008.

Heterostructure field-effect transistors (HFETs) composed of antimonide-based compound semiconductor (ABCS) materials have intrinsic performance advantages due to the attractive electron and hole transport properties, narrow bandgaps, low ohmic contact resistances, and unique band-lineup design flexibility within this material system. These advantages can be particularly exploited in applications where high-speed operation and low-power consumption are essential. In this paper, we report on recent advances in the design, material growth, device characteristics, oxidation stability, and MMIC performance of Sb-based HEMTs with an InAlSb upper barrier layer. The high electron mobility transistors (HEMTs) exhibit a transconductance of 1.3 S/mm at VDS = 0.2V and an fT Lg product of 33 GHz-microns for a 0.2 microns gate length. The design, fabrication and improved performance of InAlSb/InGaSb p-channel HFETs are also presented. The HFETs exhibit a mobility of 1500 cm2/V-sec, an f(max) of 34 GHz for a 0.2 m gate length, a threshold voltage of 90mV, and a subthreshold slope of 106mV/dec at VDS = 1.0V., Published in the Journal of IEICE Trans. Electron., vE91-C n7 p1050-1057, July 2008. Supported in part by the Office of Naval Research.

Unannealed Pd/Pt/Au contacts to p-type In0.27Ga0.73Sb were fabricated and measured. Relatively high hole mobilities, with respect to similarly doped InP-lattice-matched materials, and associated low sheet resistances were measured for the p-type In0.27Ga0.73Sb material. The unannealed Pd/Pt/Au contacts were found to be Ohmic in nature; and for a hole density of 2.9 x 10(to the 19th power) cm-3 and a mobility of 160 cm2 /V s, a specific contact resistance of 7.6 x 10(to the -8 power) Ohms cm2 was measured., Published in the Journal of Vacuum Science and Technology B, v24 n5 p2388-2390, Sep/Oct 2006.