Injection Luminescence in GaAs by Direct Hole-Electron Recombination

Luminescence from GaAs $p-n$ junctions was measured under conditions where spectral distortion due to self-absorption was ≤15%. Spectra were observed through a 2-3-μ-thick Zn-diffused $p$-type layer ($C_0\simeq 5\times {10}^{19}$ ${\mathrm{cm}}^{-3\mathrm{}}$) and a thin Au contact. Junctions in a float-zone-refined crystal, $n=2\mathrm{}\times {10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$, showed a dominant emission band with peak energies of 1.423 and 1.508 eV when measured in ambients of 298 and 77°K, respectively. This band is attributed to direct hole-electron recombination resulting from hole diffusion into the $n$-type region of these $p-n$ junctions. Supportive evidence includes good correspondence with the calculated emission peak based on detailed balancing arguments and optical absorption data, independence of peak energy on junction voltages at low current densities, and agreement with photo-luminescent data for $n$-type GaAs. The recombination process responsible for this band is significant for diodes with $n=2.3\mathrm{}\times {10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$ at room temperature, but not at 77°K, nor for diodes with $n=2\mathrm{}\times {10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$ at either temperature.