Abstract
An investigation was made of the laser energy and spectral characteristics of specially pure epitaxial GaAs films, having a carrier density of 7×1013–3×1015 cm–3, excited by a pulsed (τ≈100 nsec, ƒ=50Hz) 50 keV electron beam at temperatures 92–300°K. It was found that coherent radiation is generated as a result of the recombination of carriers which form a high-density electron-hole plasma. At 92°K, the lasing threshold was fairly low, ~0.4 A/cm2, but the differential quantum efficiency was high, ~20–25%. As the temperature increased (up to 300°K), the efficiency decreased negligibly, by a factor of 1.5–2, and jth varied as ~T3/2 . Waveguide modes, in which the radiation was completely polarized, were observed in the emission spectra of these lasers. The reasons for the formation of a waveguide on excitation of undoped GaAs are discussed.
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