Nonstoichiometric growth and cluster formation in low temperature grown GaAsSb for terahertz-applications

Nonstoichiometric low-temperature grown (LTG) GaAs0.6Sb0.4 is epitaxially grown by molecular beam epitaxy on a lattice mismatched Al0.77In0.23As buffer layer. Ex situ annealing leads to an increase in the wafer sheet resistivity. Values as high as 1.7×108Ω∕sq were measured. By high resolution transmission electron microscopy, clusters were observed in LTG-GaAs0.6Sb0.4 after annealing, some of them attached to dislocation lines. Moreover, in a 600°C annealed sample, the clusters have two different crystal structures and a spread in cluster size is present from an early formation state up to a diameter of 12.5nm. Hence, the strain surrounding the clusters is not uniform, which leads to an asymmetry of the x-ray diffraction (XRD) peak. In addition to an increased peak asymmetry with increasing annealing temperature, the XRD peak is shifted towards higher 2θ values, resulting in a lattice constant shift of 0.24%. This lattice constant shift is due to a strain relaxation process by forming clusters.

[1]  A. Gossard,et al.  State-of-the-art in 1.55 µm ultrafast InGaAs photoconductors, and the use of signal-processing techniques to extract the photocarrier lifetime , 2005 .

[2]  Shui-Qing Yu,et al.  GaAsSb/GaAs band alignment evaluation for long-wave photonic applications , 2003 .

[3]  J. W. Matthews,et al.  Defects in epitaxial multilayers: I. Misfit dislocations* , 1974 .

[4]  Hans L. Hartnagel,et al.  Low-temperature growth and post-growth annealing of GaAsSb , 2005 .

[5]  Toshiaki Kagawa,et al.  Ultrafast 1.55‐μm photoresponses in low‐temperature‐grown InGaAs/InAlAs quantum wells , 1994 .

[6]  A. Suvorova,et al.  ENHANCED PRECIPITATION OF EXCESS AS ON ANTIMONY DELTA LAYERS IN LOW-TEMPERATURE-GROWN GAAS , 1999 .

[7]  Hans L. Hartnagel,et al.  Tunable CW-THz system with a log-periodic photoconductive emitter , 2004 .

[8]  K. C. Hwang,et al.  Ultrafast long-wavelength photodetectors fabricated on low-temperature InGaAs on GaAs , 1993, IEEE Photonics Technology Letters.

[9]  A. Claverie,et al.  Local stresses induced by nanoscale As-Sb clusters in GaAs matrix , 2002 .

[10]  R. M. Cohen,et al.  Organometallic vapor phase epitaxial growth of GaAs0.5Sb0.5 , 1984 .

[11]  M. Manfra,et al.  New MBE buffer used to eliminate backgating in GaAs MESFETs , 1988, IEEE Electron Device Letters.

[12]  Arthur C. Gossard,et al.  Ultrafast photoresponse at 1.55 μm in InGaAs with embedded semimetallic ErAs nanoparticles , 2005 .

[13]  Hartmut Fuess,et al.  Structure investigation of low-temperature-grown GaAsSb, a material for photoconductive terahertz antennas , 2005 .

[14]  A. Gossard,et al.  Microstructure and electronic characterization of InGaAs containing layers of self-assembled ErAs nanoparticles , 2002 .