Recombination coefficients of GaN-based laser diodes

Abstract

We measure the charge carrier recombination coefficients of InGaN quantum wells by analyzing the dynamical properties of (Al,In)GaN laser diodes emitting in the violet spectral range. Relaxation oscillations and turn-on delays are fitted to a rate equation model including a charge carrier density dependent recombination rate. Using optical gain spectroscopy we can directly determine the injection efficiency of the devices and thereby separate the effect of charge carrier leakage from that of carrier recombination. We find a third-order recombination coefficient of (4.5+/-0.9) x 10(-31) cm(6)s(-1) which is in agreement with theoretical predictions for phonon- and alloy-disorder-assisted Auger scattering

First-principles calculations of indirect Auger recombination in nitride semiconductors

“…for E gap = 3.5 eV) and the corresponding coefficients cannot account for the experimentally measured values in nitride devices (10 −31 -10 −30 cm 6 s −1 ) [3][4][5][6][7][8][9][10][11]. The coefficients increase drastically for decreasing band-gap values in the range of 2.4-3.5 eV, which is the typical band-gap range for nitride devices.…”

“…Figure 16 illustrates that charged-defect-assisted Auger recombination is weak for realistic densities of charged defects. Even if we assume a concentration of 10 19 cm −3 of triply charged defects (Z = 3, the charge state expected for gallium vacancies in n-type GaN), the calculated charged-defect-assisted Auger coefficients increase only by a factor of 9 and are still smaller by one order of magnitude compared to the phonon-assisted results. In order to get an effect comparable to phononassisted Auger, the defect density would need to be on the order of 10 21 cm −3 of singly charged defects or 10 20 cm…”

“…As a result, it becomes an important carrier recombination mechanism at high carrier densities and reduces the efficiency of solid-state light emitters at high currents. In particular, Auger recombination has been shown to be involved in the efficiency reduction of nitride LEDs and lasers at high power [2][3][4][5][6][7][8][9][10][11][12][13]. The direct Auger recombination process [ Fig.…”

Modulation bandwidth studies of recombination processes in blue and green InGaN quantum well micro-light-emitting diodes

“…For the present we assume this to be independent of the injection current; this will be discussed later. A value of 0.7 is used as reported by Scheibenzuber et al 7 based on slope efficiency measurements of GaN-based laser diodes. The measured carrier lifetimes are plotted against the carrier densities obtained in this way in Fig.…”

“…5 There is much controversy over the physical mechanisms causing droop. Suggested candidates for this include Auger recombination, 6,7 carrier overflow, 8,9 and unusual defect behavior. 10,11 To engineer devices with high efficiencies or those capable of being modulated at high rates, a thorough understanding of the physics governing the carrier density dependence of non-radiative processes in GaN LEDs is needed.…”