ANNEALING EFFECT ON THE P-TYPE CARRIER CONCENTRATION IN LOW-TEMPERATURE PROCESSED ARSENIC-DOPED HGCDTE

We report the results of annealing effects on the As-doped alloy HgCdT e grown by molecular beam epitaxy (MBE), arsenic (As) diffusion in HgC dTe from Hg-rich solutions at low temperatures, and As ion implantatio n at room temperature. Hall-effect measurements, secondary ion mass sp ectrometry and p-on-n test photodiodes were used to characterize the A s activation. High As-doping levels (10(17)-10(19) cm-3) could be obta ined using either MBE growth, As diffusion or As ion-implantation. Ann ealed below 400-degrees-C, As doping in HgCdTe shows n-type characteri stics, but above 410-degrees-C demonstrates that all methods of As dop ing exhibit p-type characteristics independent of As incorporation tec hniques. For example, for samples annealed at 436-degrees-C (P(Hg) app roximately 2 atm), in addition to p-type activation, we observe a sign ificant improvement of p/n junction characteristics independent of the As source; i.e. As doping either in situ, by diffusion, or ion implan tation. A study of this As activation of As-doped MBE HgCdTe as a func tion of anneal temperature reveals a striking similarity to results ob served for As diffusion into HgCdTe and implanted As activation as a f unction of temperature. The observed dependence of As activation on pa rtial pressure of Hg at various temperatures in the range of 250 to 45 0-degrees-C suggests that As acts as an acceptor at high Hg pressure ( > 1 atm) and as a donor at low Hg pressure (< 1 atm) even under Hg-ric h conditions.