<title>Carrier escape time in GaAs/AlGaAs and InGaAs/GaAs quantum well lasers</title>

Abstract

The transport of carriers along the confinement region, the carrier capture into, and the carrier escape out of the quantum wells (QWs) are limiting processes affecting the high-frequency properties of QW lasers. The influence of these processes on the laser performance depends mainly on the ratio of the effective carrier transport/capture time and the effective escape time. We present experimental results about the escape times for GaAs/AIGaAs and InGaAs/GaAs high-speed QW lasers with varied geometrical dimensions (cavity width and length), number of QWs, In-concentrations, and p-doping levels in the active region, as extracted from electrical impedance measurements in the sub-threshold regime. In addition to the expected increase of the escape time with increasing QW barrier height, we observe an important increase in the escape time for lasers with p-doping. The escape time dependences on the carrier concentration and on the temperature are determined and discussed.

Carrier dynamics and microwave characteristics of GaAs-based quantum-well lasers

“…Above threshold: (15) and . In this case, the only influenc on the modulation response is an additional low-pass filte with the time constant , whereas the expressions for the relaxation frequency and the damping rate are not modifie by the carrier capture/transport and re-emission processes.…”

“…6 indicates an upper or lower limit: ns for a p-doped In Ga As MQW and ns for undoped In Ga As MQW devices. A more detailed characterization in terms of of the above samples and of other laser devices with different epitaxial structures was presented in [15].…”

Impact of Carrier Transport and Capture on VCSEL Dynamics

“…the choice of materials and associated diffusion coefficients, the length of the SCH, and the energy spacing between QW subbands with respect to the LO phonon energy. Another important time constant is the carrier escape time from QWs which quantifies the rate at which carriers confined in the QWs are thermally excited back to the continuum of unconfined states in the SCH [6]. In addition, time constants related to spontaneous recombination in the SCH and the QWs [7], as well as leakage of carriers out of the SCH [8], are important for QW laser dynamics.…”

Carrier capture and escape processes in In/sub 0.25/Ga/sub 0.75/As-GaAs quantum-well lasers

“…In In Ga As-GaAs lasers the escape time is expected to decrease with decreasing indium concentration, due to the exponential dependence of the escape time on the effective barrier height [3], [4]. This decrease can have dramatic consequences on the modulation bandwidth of these structures if the condition is no longer valid.…”

“…2, where this behavior is compared with the theoretical linear dependence of on [14] (dotted line). This superlinear dependence is attributed to the exponential dependence of on the inverse of the temperature [3], [4]:…”