Lateral carrier sweep-out in multi-quantum well optoelectronic devices

The frequency response of multi-quantum well (MQW) optoelectronic devices is governed by the rate of carrier injection and removal from the active regions. In a conventional p-i-n structure vertical rate limiting carrier transport mechanism is primarily due to thermionic emission of holes and electrons from the quantum wells. However, in waveguide structures the p and n contacts can be in-diffused on either side of the waveguide. With an applied reverse electrical bias, lateral transport of the carriers by diffusion and drifting is accomplished without the need to overcome any energy potential barrier. Since the waveguide geometry can be very small (~1 μm), the time taken for the carriers to traverse that region is inherently fast and hence high speed devices can readily be achieved