We report on the growth and characterization of InAs∕GaSb superlattice light emitting diodes (LEDs) operating in the midwave infrared at 3.8μm at 77K. Devices were grown by solid source molecular beam epitaxy on (100) GaSb substrates and were fabricated into 120×120μm2 mesa devices using wet etching. By employing an eight-stage cascaded active region design, output powers in excess of 1.5mW were achieved at 77K with 100mA peak drive current and a 50% duty cycle. Operating characteristics of the devices were examined from room temperature to 77K under quasi-dc excitation conditions.

The performances of a pin versus a pn structure from GaInAsSb materials operating at room temperature are compared both from a theoretical point of view and experimentally. Theoretically, it is found in materials limited by generation-recombination currents, pn junctions have a higher D* than pin junctions. The thinner depletion region of pn junctions results in a lower responsivity but a higher dynamic resistance, giving an overall higher D* compared to a pin structure. A series of five p+pn+ Ga0.80In0.20As0.18Sb0.82 detector structures latticed matched to GaSb substrates and with 2.37 mu m cut off wavelength were grown by molecular beam epitaxy and processed into variable size mesa photodiodes. Only the doping of the absorbing (p) region was varied from sample to sample, starting with nominally undoped (similar to 1x10(16) cm(-3) p-background doping due to native defects) and increasing the doping until a p+n+ structure was attained. Room temperature dynamic resistance-area product R(0)A was measured for each sample. A simple method is presented and used to disentangle perimeter from areal leakage currents. All five samples had comparable R(0)A's. Maximum measured R(0)A was 30 Omega-cm(2) in the largest mesas. Extracted R(0)A's in the zero perimeter/area limit were about similar to 50 Omega-cm(2) (20-100 Omega-cm(2)) for all samples. Within uncertainty, no clear trend was seen. Tentative explanations are proposed.

We report the demonstration of room temperature gate control over the electron spin dynamics using the Rashba effect in a (110) InAs∕AlSb two-dimensional electron gas. Our calculations predict that the strong spin–orbit interaction in this system produces pseudomagnetic fields exceeding 1 T when only 140 mV is applied across a single quantum well. Using this large pseudomagnetic field, we demonstrate low-power spin manipulation on a picosecond time scale. Our findings are promising for the prospect of nonmagnetic low-power, high-speed spintronics.