PLASMA DAMAGE AND ACCEPTOR PASSIVATION IN D2-PLASMA-TREATED INPZN - A PHOTOLUMINESCENCE AND ELLIPSOMETRY STUDY

Deuteration of Zn-doped InP was performed by indirect exposure of the InP surface to a remote D2 glow-discharge plasma. The dopant passivation and plasma-induced defects were investigated by photoluminescence (PL) and spectroscopic ellipsometry as a function of temperature, T(pt), during plasma treatment in the range 30-220-degrees-C. It is found that low T(pt) causes weak surface alteration whereas high T(pt) leads to preferential etching of P and the formation of In islands. At an intermediate deuteration temperature T(pt)=90-degrees-C, the surface is less affected by the plasma treatment compared to any other T(pt). In addition, a broad, low-energy PL band in the range 1.24-1.34 eV shows up. These results are explained by the in-diffusion of P vacancies (V(p)) created at the surface and the subsequent formation of P vacancy-related defects in the bulk of InP. Complexes such as (V(p)+Zn(ln)-) are believed to form and yield the PL band, in analogy with earlier PL studies on GaAs:Zn. The results of secondary-ion mass spectrometry and effusion measurements indicate that the diffusion of D proceeds by trapping on the Zn atoms, thus confirming the dopant passivation seen by PL measurements. In addition, the sample treated at 90-degrees-C contains a significant fraction of excess deuterium near the surface, which passivates the plasma-induced recombination centers. Additional centers are observed in InP deuterated between 90-degrees-C and 170-degrees-C. These centers can be partly annealed by laser irradiation at 77 K. The resulting strong enhancement of the low-energy PL band is interpreted as being due to the rearrangement of V(p)-related recombination centers into V(p)-related radiative centers assumed to be V(p)+Zn(In)-.