  The quantum efficiency of double hetero-junction light-emitting diodes (LEDs)
can be significantly enhanced at low current density by tailoring the spatial
profile of dopants to suppress Shockley-Read-Hall (SRH) recombination. To
demonstrate this effect we model, design, grow, fabricate, and test a GaInAsP
LED ($\lambda \approx$ 1330nm) with an unconventional dopant profile. Compared
against that of our control design, which is a conventional $n^+$-$n$-$p^+$
double hetero-junction LED, the dopant profile near the $n$-$p^+$
hetero-structure of the new design displaces the built-in electric field in
such a way as to suppress the J02 space charge recombination current. The
design principle generalizes to other material systems and could be applicable
to efforts to observe and exploit electro-luminescent refrigeration at
practical power densities.
