The CdZnTe-based and GaAs-based HgCdTe epilayers were grown by liquid phase epitaxy and molecular beam epitaxy, respectively, and then coated by CdTe layers as barrier cap layers for ion implantation. Subsequently, arsenic ions were implanted into the samples at different implant energies, and the two-step high temperature annealing under Hg overpressure was operated on as-implanted samples to eliminate induced damages and activate arsenic ions. After thinning the as-implanted and annealed samples by ion milling, the microstructure of lattice defects in arsenic-implanted and annealed HgCdTe was characterized by high resolution transmission electron microscopy (HRTEM), while the arsenic profiles were measured by secondary ion mass spectroscopy (SIMS). By X-ray diffraction (XRD), the influences of pre-annealing, ion implantation and post-annealing on lattice structure were studied. The experimental results indicate that the implant induced defects underneath the amorphized layer contain dislocation clusters and dislocation lines. For the implant energy of 450keV, a residual point defect belt was observed around the previous amorphous/crystal (a/c) interface in the as-implanted sample after annealing, implying that the recrystallization occurs from surface towards a/c interface. The HRTEM observation of the point defect shows that the defect is a cluster of vacancies in fact. Also, the ion implantation not only broadens the XRD peak, but also makes the peak deviation and split. It indicates that the introduction of atomic stress changes the lattice constant, thereby leading to the peak deviation.
The barrier cap layer (BCL) is considered to be able to absorb partially implant induced damages during ion implantation, thus its structure and property could impact the result of ion implantation. In this paper, for As ion implantation in HgCdTe, the different BCLs were deposited on the CdZnTe-based (LPE) and GaAs-based (MBE) HgCdTe epilayers, respectively. Then, the influences of thicknesses and structures of these BCLs on dopant profiles and implant damages were investigated. The as-grown BCLs include thermally evaporated (TE) ZnS, TE CdTe, electron beam evaporated (EBE) CdTe and in-situ CdTe/ZnTe grown by MBE. The SIMS profiles and TEM characterization indicate: For TE ZnS BCLs, there exists an optimized thickness to obtain the deepest As indiffusion after high temperature annealing, and the end-of-range (EOR) depth is linearly proportional to the thickness ratio of a-MCT layer/damage layer. For TE CdTe BCLs, the barrier layer induced channeling effect (BLICE) occurs to the thin BCL samples, while this effect is suppressed in the thick BCL samples. The phenomenon might be due to that the blocking effect of the layered structure inside each crystal column becomes dominate in the thick BCL samples. Additionally, the EBE CdTe BCL with layered structure can suppress effectively the BLICE effect; in the in-situ CdTe/ZnTe BCL, the short defect layer generated in the CdTe buffer layer and the amorphization of the ZnTe layer during ion implantation also play a significant role in suppressing the BLICE effect.