Minority carrier lifetime and luminescence efficiency of 1.3 µm InGaAsP-InP double heterostructure layers

Minority carrier lifetimes and quantum efficiencies were measured for a series of 1.3 μm InGaAsP active layers. Radiative and nonradiative components of lifetime as a function of electron and hole density were determined from this data. The measured lifetimes were
T \approx 26
(10
¹⁸
cm
^-3
/p)
^1.2
ns for p-type, and
T \approx 33
(10
¹⁸
cm
^-3
/n)
^0.8
ns for n-type material. The drop in efficiency with doping is consistent with the ratio of nonradiative and radiative rates being proportional to carrier density. The nonradiative and radiative rates are equal at
p = (2.5 \pm 0.9)10^{18}
cm
^-3
and
n = (3.3 \pm 0.7)10^{18}
cm
^-3
. A lifetime of 200 ns was observed for an undoped sample with a 0.2 μm thick active layer. The long lifetime shows that recombination with background traps is quite small, and that the interface recombination velocity is less than 50 cm/s, an order of magnitude less than for AlGaAs-GaAs double heterostructures. The minority carrier lifetime increases with temperature in lightly doped samples, as expected for radiative recombination, and shows little change with temperature in heavily doped samples. If the measured nonradiative rate is assumed to be due to the free carriers and not due to doping related traps, it can nearly account for the temperature dependence of laser threshold currents and for light-emitting diode efficiency.