Germanium diffusion with vapor-phase GeAs and oxygen co-incorporation in GaAs

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.

Enhanced photoemission from surface modulated GaAs:Ge

“…[28] Ge diffused in GaAs will tend to act as a donor in GaAs. [22,28] , where the Ge in-diffusion depth of up to hundreds of nanometers has been reported [7,26,29] and is dependent on annealing time and temperature. Surface modulation on nanoscale may be brought up on a Ge surface by annealing a thin Ge-layer on GaAs substrate.…”

“…In contrast, use of other group IV elements involve some fundamental problems associated with large lattice mismatch (∼4% for silicon) and different thermal expansion coefficients. In-diffusion of Ge in GaAs [7,22,23] can results in GaAs 1-x Ge x structures [20,23] exhibiting direct band-gap with superior optical properties. [19] For semiconductors, bringing the structure down to nanoscale may fundamentally modify the properties of materials by inducing low-dimensional charge carrier confinement [24] and self-assembling, allowing the growth of well-defined random or aligned nano/quantum structures [24] without the need of sophisticated lithography techniques.…”

“…[24] Nanostructuring processes may be brought about by thermal treatment at temperature below the melting point of the material used. [25] Among challenges faced with integration of Ge and GaAs are [21,26] formation of anti-phase boundaries (APD) and interdiffusion of Ge, [27] O, [22] Ga and As at the interfaces or the surface. [28] Ge diffused in GaAs will tend to act as a donor in GaAs.…”

Effect of germanium auto-diffusion on the bond lengths of Ga and P atoms in GaP/Ge(111) investigated by using X-ray absorption spectroscopy

“…Interestingly, the important factor of auto-diffusion of Si and Ge substrate materials on the grown III-V epitaxial structures are investigated to a lesser extent. Some of the work has reported that auto-diffused Si and Ge can occupy both the Ga and As sites in GaAs layers, grown by metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE), depending on the growth conditions (Dunlap Jr, 1954;Galiana et al, 2008;Wang et al, 2018;Gupta & Khokle, 1985). Also, by the increased amount of auto-diffusion of group IV elements into the III-V layer, the free carrier density starts reducing due to the charge carrier compensation.…”

“…In a recent work, it was reported that auto-diffused Ge into GaAs epilayer acts as an n-type dopant when grown at 860 C. The dopant density due to Ge diffusion at high temperature (860 C) in GaAs can be very high, >> 10 18 cm À3 . The thermal activation energy of the defect centers formed by the diffused Ge and the gallium vacancies (Ge Ga -V Ga ) are estimated from configurational coordination modeling (Wang et al, 2018). The auto-diffusion can be reduced by growing the barrier layer at low temperature, $ 475 C, with reduced time duration of growth (Galiana et al, 2008).…”