Abstract
Vapor-phase germanium diffusion has been demonstrated in Zn-doped and semi-insulating GaAs in sealed ampoules with GeAs powders and excess arsenic. Secondary-ion-mass spectroscopy (SIMS) profiles indicate the presence of unintentional co-incorporation of oxygen in high densities (>1017/cm3) along with diffused germanium donors whose concentration (>>1018/cm3) determined by electro-chemical capacitance-voltage (ECV) profiler shows significant compensation near the surface. The source of oxygen mainly originates from the GeAs powder which contains Ge-O surface oxides. Variable-temperature photoluminescence (PL) shows that in GeAs-diffused samples, a broad peak ranging from 0.86-1.38 eV with the peak position around 1.1 eV predominates at low temperatures while the near band-edge luminescence quenches. The broad band is attributed to the GeGa-VGa self-activated (SA) centers possibly associated with nearby oxygen-related defect complex, and its luminescence persists up to 400 K. The configurational-coordinate modeling finds that the SA defect complex has a thermal activation energy of 150-180 meV and a vibrational energy 26.8 meV. The presence of oxygen does not much affect the SA emission intensity but may have influenced the peak position, vibration frequency and activation energy as compared to other common donor-VGa defects in GaAs.
Highlights
Si is by far the most common n-type impurity in GaAs incorporated either during growth[1–4] or in post-growth processing.[5–8] Unlike Zn which forms high-vapor ZnAs2 or Zn2As3 conveniently employed to introduce Zn diffusion in GaAs/AlAs heterostructures,[9,10] Si lacks a SiAs counterpart so most Si is incorporated in solid phase
Oxygen is known as a deep trap in GaAs and its trap states may vary depending on the choice of oxygen-containing sources of Ga2O3, As2O3 in the melts[12] or intentional precursors in metalorganic vapor phase epitaxy (MOVPE).[1,2,13–17]
For capless samples annealed along with germanium arsenide (GeAs) powder and arsenic, a broad defect peak (0.86eV to 1.38eV) appears in the PL spectra while the near band edge luminescence quenches, and the broad peak decreases in intensity with temperature
Summary
Si is by far the most common n-type impurity in GaAs incorporated either during growth[1–4] or in post-growth processing.[5–8] Unlike Zn which forms high-vapor ZnAs2 or Zn2As3 conveniently employed to introduce Zn diffusion in GaAs/AlAs heterostructures,[9,10] Si lacks a SiAs counterpart so most Si is incorporated in solid phase. Si is by far the most common n-type impurity in GaAs incorporated either during growth[1–4] or in post-growth processing.[5–8]. Unlike Zn which forms high-vapor ZnAs2 or Zn2As3 conveniently employed to introduce Zn diffusion in GaAs/AlAs heterostructures,[9,10] Si lacks a SiAs counterpart so most Si is incorporated in solid phase. On the other hand, does form GeAs, which allows vapor-phase Ge diffusion to be realized. Few have reported to employ vapor-phase Ge diffusion other than Deppe et al.[11] who have evaporated Ge onto GaAs substrate to provide Ge or GeAs vapor at high temperatures. A major focus in this work is to introduce Ge diffusion in GaAs through vapor-phase germanium arsenide. Electrical and optical properties, regarding the self-activated luminescence and thermal quenching[19,20] in the Ge and oxygen co-doped GaAs are presented
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