Effect of V/III ratio on the optical properties of LPMOVPE grown undoped GaAs epi-films

Low temperature photoluminescence spectroscopy is used extensively to study the distribution of defects, concerning the type and impurity in a semiconductor film. Typical photoluminescence spectra are observed in a near band edge region. The undoped GaAs epitaxial layers grown by low pressure metal organic vapor phase epitaxy under different V/III ratios, an optimum ratio corresponding to a minimum number of shallow impurities was clearly identified. The V/III ratio has strong effect on the optical properties of undoped GaAs epitaxial layers. When the V/III ratio was varied from 45 to 87, the electron concentration, n, of undoped GaAs increased with increasing V/III ratio. Below the V/III ratio of 45 in our case, the sample exhibited a p-type behavior, which has been identified by photoluminescence as well as depth profiling by Electro-chemical Capacitance Voltage (ECV) profiler.