Observation of the upper branch (N′Γ) of the nitrogen isoelectronic trap in GaAs1−yPy

Abstract
Luminescence data are presented on nitrogen‐doped GaAs1−yPy in the composition region 0.38≲x≲0.47, near the direct‐indirect crossover (yc?0.45, 77 °K), which permit the identification of the upper branch, N′Γ, of the N trap. The existence of such a state has been predicted by a recent theory of the N trap that includes both the long‐range (Vl) and short‐range (Vs) character of the isoelectronic impurity potential in III–V alloys. The N′Γ state is observed to lie in the band gap for 0.40≲y≲0.47 and is a resonant state in the Γ continuum for yN′Γ and NΓ states (the latter becoming the short‐range state N for y≳0.42), along with previous work demonstrating laser operation on the low‐energy NX state, shows that all three N‐trap states have sufficient oscillator strength for laser operation if the Γ‐N separation is small enough for band‐structure enhancement to be efffective.