Influence of a single InGaAs quantum well on current transport and deep levels in GaAs

An comprehensive study of the effects of tunneling on the I-V characteristics and the deep level trap spectroscopy was conducted on GaAs/In_xGa_1-xAs/GaAs single quantum wells (SQWs) with different indium composition (x = 0.15, 0.24) and well width (t_w = 80, 200 A ̊) by temperature-varying current-voltage characteristics (I-V-T), deep level transient spectroscopy (DLTS) and photoreflectance (PR) spectroscopy. By the correlated analyses, we found that the tunneling emissions have obvious effects on the I-V characteristics and the DLTS spectra. The I-V-T measurements revealed clear effects of SQWs on the overall current flow. Thermionic field emission (TFE) was observed at low temperature and low voltage bias regions. The magnitude of the current of the samples with thinner quantum well width was found to be higher than that with thicker well width because of the higher tunneling probability of electrons from the SQWs. The DLTS spectra showed a typical plateau-like feature which was attributed to the tunneling emission from the InGaAs quantum well. A hole trap, H1, with activation energy ΔE_a = 0.52-0.56 eV was also observed for all samples. We relate this hole trap to the gallium vacancies in the GaAs bulk. The photoreflectance spectra showed an obvious absorption feature which corresponds to the transitions in the In_xGa_1-xAs SQWs.