Study of deep levels in GaAs $p$–$i$–$n$ structures

An experimental study of the capacitance–voltage ($C$–$V$) characteristics and deep-level transient spectroscopy (DLTS) of $p^{+}$–$p^{0}$–$i$–$n^{0}$ structures based on undoped GaAs, grown by liquid-phase epitaxy at two crystallization-onset temperatures $T_b$ (950 and 850$^\circ$C), with optical illumination switched off and on, are performed. It is shown that the $p^0$, $i$, and $n^0$ layers of epitaxial structures are characterized by the presence of defects with deep donor- and acceptor-type levels in concentrations comparable with those of shallow donors and acceptors. Interface states are found, which manifest themselves in the $C$–$V$ characteristics at different measurement temperatures and optical illumination; these states form an additive constant. A distinct temperature dependence of the steady-state capacitance of the structures is revealed. It is found that the injection of minority carriers under an applied positive filling pulse and optical recharging lead to modification of the structure and, correspondingly, the DLTS spectra of the $p^{+}$–$p^{0}$–$i$–$n^{0}$ structures. It is revealed that the $p^{+}$–$p^{0}$–$i$–$n^{0}$ GaAs structures grown at $T_b$ = 850$^\circ$C are characterized by a lack of interface states and that the recharging of acceptor-type deep traps under illumination does not change the $C$–$V$ characteristics. The conventionally measured DLTS spectra reveal the presence of two hole traps: $HL5$ and $HL2$, which are typical of GaAs layers.