<title>Effect of V/III ratio on extended defects in InGaAlP measured by isothermal DLTS</title>

Abstract

Deep level transient spectroscopy (DLTS) characterization of defects in InGaAlP films grown using two different V/III ratios was carried out. Electron trap levels with activation energies of 0.42 eV and 0.78 eV were detected in the sample with V/III ratio of 50 and 75 respectively, using isothermal DLTS. In this paper, the severe temperature dependence of the DLTS signals observed for these two trap levels is explained in terms of the presence of noticeable capture barriers for electrons. The capture barrier heights of 0.27 and 0.13 eV were estimated for trap levels of 0.42 eV and 0.78 eV respectively. It is believed that these two trap levels are associated with extended defects based on the observation of logarithmic dependence of the DLTS signal on filling pulse width. This is further supported by the observation of a broader temperature scan spectrum in the sample with V/III ratio of 75. For the sample with a V/III ratio of 50, a monotonic increase in DLTS signal with temperature was observed for temperature scan DLTS up to the upper limit of the system. Although the two defect levels observed in this study appear both to be related to extended defects, they are related to two different defects simply due to the observation of much different thermal signatures for these two defects. The results indicate that a V/III ratio of 50 is a better choice as the associated defect has a smaller capture cross-section and a larger capture barrier.