DEEP ELECTRON TRAPS IN AlAs-GaAs SUPERLATTICES AS STUDIED BY DEEP-LEVEL TRANSIENT SPECTROSCOPY.

Deep electron traps in Si-doped AlAs-GaAs superlattices (SLs) grown by MBE have been investigated using deep-level transient spectroscopy (DLTS). The concentration of the characteristic electron trap (E2 trap) in the SLs increases upon decreasing the period of SL and increasing the Si doping concentration. The E2 trap concentration for uniformly Si-doped SLs is more than one order higher than that for SLs doped selectively at the middle part of each AlAs and GaAs layer. The E2 traps have properties similar to the so-called DX centers in Al//xGa//1// minus //xAs, and they exist only in the AlAs-GaAs interfaces. The different activation energies of the traps in SLs and Al//0//. //3Ga//0//. //7As can be explained in terms of carrier emission from the E2 trap to the mini-band levels of the SLs and to the conduction band minimum of the alloys, respectively.