The peculiar correlationship between the optical localization-state and the electrical deep-level defect-state was observed in the In_0.52Al_0.48As/In_0.53Ga_0.47As quantum well structure that comprises two quantum-confined electron-states and two hole-subbands. The sample clearly exhibited the Fermi edge singularity (FES) peak in its photoluminescence spectrum at 10–300 K; and the FES peak was analyzed in terms of the phenomenological line shape model with key physical parameters such as the Fermi energy, the hole localization energy, and the band-to-band transition amplitude. Through the comprehensive studies on both the theoretical calculation and the experimental evaluation of the energy band profile, we found out that the localized state, which is separated above by ~0.07 eV from the first excited hole-subband, corresponds to the deep-level state, residing at the position of ~0.75 eV far below the conduction band (i.e., near the valence band edge).

Mobility spectrum analysis (MSA) is a method that enables the carrier density (and mobility) separation of the majority and minority carriers in multicarrier semiconductors, respectively. In this paper, we use the p-GaAs layer in order to demonstrate that the MSA can perform unique facilities for the defect analysis by using its resolvable features for the carriers. Using two proven methods, we reveal that the defect state can be anticipated at the characteristic temperature $T_{deep},$ in which the ratio ($R_{N_n/N_h}$) that is associated with the density of the minority carrier $N_n$, to the density of the majority carrier $N_h$, exceeds 50%. (1) Using a p-GaAs Schottky diode in a reverse bias regime, the position of the deep level transient spectroscopy (DLTS) peak is shown directly as the defect signal. (2) Furthermore, by examining the current–voltage–temperature (I–V–T) characteristics in the forward bias regime, this peak position has been indirectly revealed as the generation–recombination center. The DLTS signals are dominant around the $T_{deep}$, according to the window rate, and it has been shown that the peak variation range is consistent with the temperature range of the temperature-dependent generation–recombination peak. The $T_{deep}$ is also consistent with the temperature-dependent thermionic emission peak position. By having only $R_{N_n/N_h}$ through the MSA, it is possible to intuitively determine the existence and the peak position of the DLTS signal, and the majority carrier’s density enables a more accurate extraction of the deep trap density in the DLTS analysis.

We propose and demonstrate that temperature-dependent curve-fitting error values of the Schottky diode I–V curve in the forward regime can be an auxiliary diagnostic signal as the temperature-scan Capacitance DLTS (CDLTS) signals and helps to work time-efficiently with high accuracy when using the Laplace Transform (LT)–DLTS or Isothermal Capacitance transient spectroscopy (ICTS) method. Using Be-doped GaAs showing overlapping DLTS signals, we verify that the LT–DLTS or ICTS analysis within a specific temperature range around the characteristic temperature $T_{peak}$ coincides well with the results of the CDLTS and Fourier Transform DLTS performed within the whole temperature range. In particular, we found that the LT–DLTS signals appeared intensively around $T_{peak}$, and we confirmed it with the ICTS result. The occurrence of the curve fitting error signal is attributed to the relatively increased misfit error by the increased thermal emission from the deep-level trap in the case near the $T_{peak}$, because the applied transport model excludes defect characteristics.