X.G. Xu

TYPE II PHOTOLUMINESCENCE AND CONDUCTION BAND, OFFSETS OF GAASSB/INGAAS AND GAASSB/INP HETEROSTRUCTURES GROWN BY METALORGANIC VAPOR PHASE EPITAXY

The optical properties of lattice-matched GaAsSb/InGaAs/InP heterostructures with a varying InGaAs layer thickness (0–900 A) were investigated. These structures display strong low temperature type II luminescence, the energy of which varies with the InGaAs layer thickness and ranges from 0.453 to 0.63 eV. The type II luminescence was used to determine directly and accurately the conduction band offset of these structures. The values obtained herein are 0.36 and 0.18 eV at 4.2 K for the GaAsSb/InGaAs and GaAsSb/InP heterojunctions, respectively, with the GaAsSb conduction band higher in energy.

Heavily carbon-doped GaAsSb grown on InP for HBT applications

We present the results of Hall measurements on heavily carbon-doped GaAsSb epilayers grown by metalorganic chemical vapour deposition (MOVPE) on InP substrates. An extremely strong alloy scattering e!ect is observed in this material, dominating the Hall mobility even at doping levels in the 1019 range. This e!ect is due to the very large (1 eV) valence band o!set between GaAs and GaSb. Despite the strong alloy scattering, conductivities as high as 890 S/cm were observed at doping levels above 1020 cm~3. CCl 4 and CBr 4 were investigated as p-type dopants. Hole concentrations of up to 1.4]1020 and 3.0]1020 cm~3 were obtained at growth temperatures of 5603C and 5003C, respectively. For both carbon sources, a strong reduction in growth rate and Sb incorporation rate was observed with increasing dopant concentration at 5603C. Carbon incorporation was observed to increase linearly with Sb solid phase mole fraction. ( 2000 Elsevier Science B.V. All rights reserved.

InP/GaAsSb/InP double HBTs: a new alternative for InP-based DHBTs

We report on the physical operation and performance of MOCVD-grown abrupt heterojunction InP/GaAs/sub 0.51/Sb/sub 0.49//InP double heterojunction bipolar transistors (DHBTs). In particular, the effect of the InP collector thickness on the breakdown voltage and on the current gain cutoff frequency is assessed and a f/sub T/ of 106 GHz is reported for a DHBT with a 400 /spl Aring/ base and a 2000 /spl Aring/ InP collector with a BV/sub CEO/ of 8 V. We show that InP/GaAsSb/InP DHBTs are characterized by a weak variation of f/sub T/ as a function of temperature. Finally, we also demonstrate that high maximum oscillation frequencies f/sub MAX/>f/sub T/ can be achieved in scaled high-speed InP/GaAsSb/InP DHBTs, and provide estimates of the maximum cutoff frequencies achievable for this emergent but promising material system. Recent results on improved structures validate our performance predictions with cutoff frequencies well beyond 200 GHz.

Metalorganic vapor phase epitaxy of high-quality GaAs0.5Sb0.5 and its application to heterostructure bipolar transistors

We report the growth and characterization of high-quality InP/GaAs0.5Sb0.5/InP heterostructures and their application to double-heterojunction bipolar transistors (DHBT). The GaAs0.5Sb0.5 layer quality was evaluated by high-resolution x-ray diffraction (XRD), low-temperature photoluminescence (PL), and atomic force microscopy (AFM). The observed 4.2 K PL linewidth was 7.7 meV and XRD rocking curves matched those of dynamical scattering simulations. In contrast to previously reported InP/GaAs0.5Sb0.5/InP DHBTs, the present devices show nearly ideal base and collector currents, low turn-on and collector offset voltages, and a high current gain. Self-aligned DHBTs exhibit a cutoff frequency over 75 GHz and common-emitter current gain greater than 100 at 300 K.

Design and performance of InP/GaAsSb/InP double heterojunction bipolar transistors

We report a fabrication technique for 1 μm wide emitter finger InP/GaAs0.51Sb0.49/InP double heterojunction bipolar transistors (DHBTs). In this technology, we use a wet-etched undercut airbridge technique to provide device isolation while minimizing parasitics and avoiding damage to semiconductor layers by dry etching. The metalorganic chemical vapor deposition-grown InP/GaAs0.51Sb0.49/InP NpN structure takes advantage of a staggered (“type II”) band lineup at InP/GaAs0.51Sb0.49 interfaces: in this material system the GaAs0.51Sb0.49 base conduction band edge lies 0.18 eV above the InP collector conduction band, thus enabling the implementation of InP collectors free of the collector current blocking effect encountered in conventional Ga0.47In0.53As base DHBTs. The structure results in very low collector current offset voltages, low emitter-base turn-on voltages, and very nearly ideal base and collector current characteristics with junction ideality factors of nB=1.05 and nC=1.00 and DHBTs with cutoff fre...

Photoreflectance study of phosphorus passivation of GaAs (001)

We present a study of the effect of phosphorus passivation on the surface electric field of undoped GaAs using photoreflectance spectroscopy. Surface electric fields were determined in surface/intrinsic/n-type (s-i-n+) samples prepared with various surface phosphorus treatments. A comparison with H2S passivated films and InGaP capped layers prepared in situ in the same growth equipment is also presented. Phosphorus surface passivation was achieved by (1) exchange reaction of the GaAs surface under tertiarybutylphosphine vapor or (2) direct growth of GaP thin epitaxial layers. The total coverage of phosphorus has been estimated by x-ray diffraction techniques. We observe a maximum reduction of the surface Fermi level using epitaxially grown GaP with an effective coverage of two monolayers. Atomic force microscopy images of all passivation treatments exhibit excellent surface morphology without roughening. The passivation effects decreased somewhat over time but reductions in the Fermi level and density of ...

InP/GaAs0.51Sb0.49/InP fully self-aligned double heterojunction bipolar transistors with a C-doped base: a preliminary reliability study

Abstract A preliminary reliability study is reported for carbon-doped InP/GaAs 0.51 Sb 0.49 /InP NpN double heterojunction bipolar transistors (DHBTs) lattice-matched to InP substrates. These DHBTs take advantage of the staggered (“type II”) band lineup at InP/GaAs 0.51 Sb 0.49 interfaces: in this system, the GaAs 0.51 Sb 0.49 base conduction band edge lies 0.15–0.18 eV above the InP collector conduction band, thus enabling the implementation of InP collectors free of the collector current blocking effect encountered in conventional Ga 0.47 In 0.53 As base DHBTs. The structure results in very low collector offset voltages, low emitter-base turn-on voltages, and very nearly ideal base and collector current characteristics with excellent junction ideality factors. Cut-off frequencies in excess of 100 GHz have been measured, making InP/GaAsSb DHBTs very attractive for wireless communication systems. InP/GaAs 0.51 Sb 0.49 heterojunctions have so far received little attention in the literature, and no reliability information is available for this promising material combination. We have found that electrical stressing at moderate bias in fully self-aligned non-passivated devices results in a rapid, and reversible, degradation of device properties which is manifested through an increase of the base current ideality factor n B . On the other hand, the collector current remains unchanged, indicating that there is no dopant migration effect under the test conditions used here.

InP/GaAsSb/InP double heterojunction bipolar transistors with high cut-off frequencies and breakdown voltages

In this work, we report on the DC and microwave performance of MOCVD-grown carbon-doped InP/GaAsSb/InP double heterojunction transistors (DHBTs) with various collector thicknesses. The cut-off frequencies (and breakdown voltages) are 106 GHz (8 V), 82 GHz (10 V) and 40 GHz (15 V) for the 2000 /spl Aring/, 3000 /spl Aring/ and 5000 /spl Aring/, lightly doped collectors. The 106 GHz, which is the best f/sub T/ ever reported in this material system, is obtained while maintaining a relatively high breakdown voltage (BV/sub CEO/=8 V). The lower cut-off frequencies obtained for the 3000 /spl Aring/ and 5000 /spl Aring/, collectors are attributed to the longer transit time in the collector and also to the Kirk like limitation brought about by high current densities in the thicker collectors.

Growth of GaAsSb/InP heterostructures by OMVPE

This paper summarizes several important aspects of the growth of GaAsSb/InP heterostructures for the fabrication of high speed double heterojunction bipolar transistors (DHBTs). Some of the challenges in OMVPE growth of antimonide/phosphide compounds are discussed, including segregation, interface issues, and control of carbon at very high doping levels. We also discuss the effect of hydrogen passivation and the role of atomic ordering and compositional modulation, including its effect on electrical properties.