Direct determination of the free-carrier injection density, the free-carrier absorption, and the recombination factors in double heterostructure diodes by optical phase measurements. Part III

Abstract

Accurate phase measurements over a temperature interval on double heterostructure laser (DH) diodes provide a means to directly measure the injected free-carrier density and the free-carrier absorption as a function of the injected current. This paper describes the underlying principles and demonstrates the validity of the simple concepts. The data permit to deduce the radiative and nonradiative recombination factors in nominally undoped active layers without taking resource to luminescence measurements. The results presented on GaAs and InGaAsP lattice matched to InP DH diodes show a good overall agreement with calculations based on a heuristic model. The radiative recombination factors at room temperature are near 5.3× 10-11 and 2.0× 10-11 cm3 s-1 for GaAs and for InGaAsP with a band gap of 1.122 eV, respectively. The free-carrier absorption due to the injected carriers is strongly dispersive and proportional to the 2.3rd power of the wavelength. We show a strong temperature dependence of the free-carrier absorption that is more important in InGaAsP than in GaAs. The results are internally consistent without the need of any free parameter. The phase measurements can also be used to characterize the heat chirping of the active layers under pulsed current excitation. © 2005 American Institute of Physics.