Metalorganic Chemical Vapor Deposition Growth of High-Quality InAs/GaSb Type II Superlattices for Mid-IR Photodetector Applications
X. B. Zhang , A. Petschke, S. Mou , C. Xu , J. H. Ryou , S. L. Chuang , K. C. Hsieh, and R. D. Dupuis 1) Center for Compound Semiconductors and School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive NW, Atlanta, GA, 30332-0250, USA 2) Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA
Type-II superlattice photodetector on a compliant GaAs substrate
A type-II superlattice (SL) of InAs-InGaSb has been grown on a compliant GaAs substrate by molecular beam epitaxy. This SL was designed for photoconductive infrared (IR) detection in the long wavelength IR band. The spectral photoresponse of this SL shows a sharp onset at 76.9 meV and a corresponding cutoff wavelength at 13.9 /spl mu/m. A sixfold increase in the peak photoresponse was measured in comparison to the response from a similar SL on a standard GaSb substrate.
Atomic force microscopy study of morphology and dislocation structure of InAs and GaSb grown on highly mismatched substrates
Abstract We have studied the surface morphology and dislocation structure of InAs grown on GaAs or InP substrates and of GaSb grown on GaAs substrates by metalorganic chemical vapour deposition (MOCVD). Atomic force microscopy (AFM) has been used to determine quantitative threading dislocation densities by observing singularities in the atomic terrace structure. All layers were grown using a thin ∼ 100 nm low temperature buffer layer grown at 400°C, which was found to greatly improve surface morphology for all materials combinations studied. The lowest dislocation densities were found for thick GaSb layers on GaAs, with around 1 × 10 6 cm −2 for a 5 μm layer. While somewhat higher levels were observed for InAs (5 × 10 6 cm −2 ), the surface roughness for these films was significantly lower. In all samples the limiting factor for surface roughness is observed to be the formation of hillocks consisting of growth spirals centred on dislocations. We suggest ways in which these data may be used to calculate some fundamental MOCVD crystal growth parameters such as the critical radius for nucleation.