Carrier lifetime and recombination in 1.3 μm p-doped InAs qauntum-dot lasers

In this paper we report on carrier lifetime measurements performed on 1.3 mu m p-doped InAs quantum-dot lasers. The carrier lifetimes were determined by fitting the measured sub-threshold optical modulation response to a single pole response function, and then correcting this time constant for the diode junction capacitance to obtain the carrier lifetime. The sub-threshold frequency response curves did indeed show a single pole behavior at all the bias currents and, as expected, the extracted carrier lifetimes monotonically decrease with increasing bias currents. The differential carrier lifetime versus bias current data was then fitted, using a simple single carrier level rate equation analysis, to determine the recombination coefficients. Using this simplified analysis, the values of the recombination coefficients are found to be: A = 1.0 x 10(7) /s, B = 2.5 x 10(-11) cm(3)/s, and C = 1.1 x 10(-29) cm(6)/s at room temperature. Since, the carriers are distributed among the dots in a complicated manner that depends on bias, the lifetimes and recombination coefficients extracted using the single carrier level analysis are the effective or average values. Thus we have also built a multi-level rate equation model including the capture and escape times between various QD and wetting layer states. The multi-level rate equation model yields intrinsic recombination coefficients of A(QD) = 5.5 x 10(7) /s, B-QD = 6.5 x 10(-11) cm(3)/s, C-QD = 5.6 x 10(-29) cm(6)/s. Regardless of the model used the dominant contribution to the threshold current is found to be Auger recombination which accounts for approximately 80% of the threshold current in our 1.3 mu m p-doped QD lasers.