Simultaneous diffusion of Zn and Cd in InGaAs

Abstract

Diffusion experiments of Zn and Cd in VPE InGaAs, lattice matched to InP, are reported. A closed ampoule technique is used. For the simultaneous diffusion of Zn and Cd from a Zn,As,/Cd,As, source an increasing amount of Cd,As, results in a decreasing p-n junction depth whereas a high hole concentration (more than lo2' cm-3 at T,,,,, = 600 "C) fixed by the Zn acceptor concentration level can be realised. The Cd atoms whose interstitial diffusion coefficient is small compared with that of the Zn interstitials penetrate into the crystal as deep as the Zn atoms. These experimental results are in accordance with numerical simulations of the simultaneous diffusion in Ill-V compounds starting from the concept of an interstitial-substitutional diffusion mechanism. The diffusion method presented is suitable for the generation of shallow-and high-doped p-type regions during controllable diffusion times.

Surface analysis of InP and InGaAs after low temperature diffusion of Zinc

“…To be opto-electrically efficient, junctions require local p-type doping of the III-V material at a level higher than 5×10 17 cm −3 , with a junction depth of about 100 nm and an abrupt front. In standard processes, this kind of doping is achieved by diffusion [1,2] or implantation of zinc [3], cadmium [4] or beryllium [5] and requires annealing temperatures above 500 o C, much higher than the aforementioned compatibility limit.…”