Electroluminescence recombination from excited-state carrier populations in double-barrier resonant-tunneling structures

Electroluminescence recombination arising from electrons in both the n=1 and n=2 confined levels (E1 and E2) of the quantum well of a GaAs-${\mathrm{Al}}_{0.4}$${\mathrm{Ga}}_{0.6}$As p-n junction double-barrier resonant tunneling structure is reported. At the E2 resonance, study of the relative intensities of the E2 to E1 electroluminescence permits a quantitative determination of the relative populations (1:300) of the two levels. From this the ratio of the E1 tunneling time to the intersubband scattering time is deduced. Despite the small population of E2, we show that a significant fraction of the on-resonance current still arises from tunneling through this state.