Features of band-edge injection electroluminescence in GaN pn structures

A study of injection electroluminescence of GaN pn homostructures produced by chloride–hydride gas-phase epitaxy is presented. The epitaxial layers are doped with silicon and magnesium to obtain n-type (doping level 5 × 1018 cm−3) and p-type (doping level 1.6 × 1018 cm−3) conductivity, respectively. Injection electroluminescence was observed in the forward current range of 3 × 10−4–2 × 10−2 A (0.4–30 A/cm2) at temperatures of 300–720 K, when the current was apparently due to recombination in the space-charge region of the pn junction through a deep level near the middle of the bandgap. Two bands are observed in the electroluminescence spectra at 300 K: the band edge (shortwave) in the near ultraviolet region (hνmax ∼3.33 eV) and in the yellow region of the spectrum (hνmax ∼2.15 eV). For band-edge electroluminescence, it was found that when heated from 300 K, its intensity decreases with an activation energy of about 80 meV; the maximum shifts linearly to the long-wavelength region with a temperature with a slope of “−5.4 × 10−4 eV/K” and the energy at the maximum is 66 meV less than the bandgap; and the full width at half-maximum with heating to 430 K decreases from 235 to ∼145 meV, maintains this value to a temperature of 550 K, and then increases to 195 meV at 650 K. The quenching of band-edge injection electroluminescence at temperatures higher than room temperature may be associated with a decrease in the lifetime of nonequilibrium charge carriers during heating.