Heteroepitaxy and characterization on InxGa1-xAs(x<0.03)/GaAs and GaAs/Si

Abstract

Two kinds of heteroepitaxial systems, $In_xGa_{1-x}$($x<0.03$)/GaAs (one example of pseudo-heteroepitaxies) and GaAs/Si (one example of true heteroepitaxies) have been grown and characterized. $In_xGa_{1-x}As$ epilayers on GaAs substrate, in the range of $0<x<0.03$, have been grown by vapor phase epitaxy(VPE) using an In/Ga alloy source, and the dependence of the InAs composition of the $In_xGa_{1-x}As$ epilayers on that of the alloy source was investigated by a simple thermodynamic analysis of a halide transport system(HCl-In-Ga-$AsH_3$-$H_2$). The influence of the In content on the band gap shift, the etch pit density (EPD), and deep trap levels has been also investigated. The InAs composition, the bandgap energy shift, and electron deep traps were measured by double crystal X-ray(DCX) diffraction, low temperature photoluminescence(PL), and deep level transient spectroscopy(DLTS) technique, respectively. The calculated and experimentally obtained InAs compositions are in good agreement in the range of $x<0.03$. Though an experimental confirmation was carried out in the small region of $x<0.03$, the thermodynamic results could be applied to obtain rough estimate of the In to Ga ratio in the source required to grow $In_xGa_{1-x}As$ epilayers with a proper composition by VPE using an In/Ga alloy source. For the observation of the surface morphology by an optical microscope and the EPD by a molten KOH-NaOH etching, the cross-hatch patterns due to misfit dislocations begin to appear at the as-grown surface of $In_xGa_{1-x}As$ epilayers about x=0.01 and the EPD of the epilayer is prominently reduced at x $\sim$ 0.003. From DLTS spectra according to the In content, the most prominent electron deep traps were E4(Ec-0.58 eV) and E5(Ec-0.84 eV) levels. The E4 trap density increased with In content while the change of E5 trap density was not monotonic. The trend of E5 trap densities versus In content was very similar to that of EPDS, i.e., a minimum in EPD and this trap...