Characterization of implanted and annealed vapor phase epitaxial GaAs

Abstract

The electrical and optical properties of as-grown and implanted and annealed vapor phase epitaxial GaAs have been determined and compared by photoluminescence, transient capacitance spectroscopy, and Hall measurements. The dominant electron trap level with activation energy ΔE = 0.83 eV is observed consistently in the as-grown layers, but is not detected in the implanted layers. A second electron trap level with ΔE = 0.37±0.01 eV is also observed in some as-grown and some implanted layers. A hole trap level with ΔE = 0.86 eV which is detected in some as-grown layers with a low density compared to the carrier concentration and in most of the implanted layers with larger density is attributed to Cr. An electron trap level with ΔE = 0.53 eV detected in some implanted layers and a hole trap level with ΔE = 0.15 eV present in all the implanted layers are believed to be created due to the implant and anneal process. Room-temperature Hall electron mobilities and activated surface carrier concentrations decrease and increase, respectively, with increasing implant dose. The mobility profiles as a function of temperature (80–550 K) are markedly different for the as-grown and implanted layers, the values being lower in the latter. A detailed analysis of the mobility data including the relevant carrier scattering mechanisms indicate that the decreased mobility is due to increased ionized impurity density. Familiar peaks which are ascribed to excitonic transitions and transitions involving C and Cu-VAs complexes have been observed in the photoluminescence spectra of the as-grown crystals. Photoluminescence of implanted and annealed GaAs indicate the formation of Si acceptors.