Abstract

We report the first measurements of picosecond carrier transport in InGaAs/GaAs multiple quantum wells (MQWs) in the i region of a reverse biased p-i-n diode. A 1 ps laser pulse operating near the exciton resonance at 950 nm excites electrons and holes, which tunnel out of the wells and screen the field. This changes the transmission of a time delayed probe pulse through the quantum-confined Stark effect. Strained InGaAs/GaAs MQWs grown via MBE within the i layer of a p-i-n diode varied in number from 20 to 50, well width from 45 Å to 100 Å, and barrier width from 125 Å to 200 Å; indium concentration was either 0.13 or 0.18. Mesas of 250 μm were fabricated and contacted by 125 μm off-centered dots. The 36 μm diameter pump and probe overlapped in the center of the non-contacted region. At room temperature a MQW with 13% In, 100 Å wells, and 200 Å barrier widths, using 0.94 pJ/pulse yielded a rise time of 10 ±2 ps and enhanced diffusion times ranging from 20 to 70 ps with applied voltages varying from 0 to 12 V. We believe the rise time is limited by the transit time of carriers to the doped region. Faster times in InGaAs are expected because of the lower electron effective mass.

© 1992 Optical Society of America