DEPTH DISTRIBUTION OF REACTIVE ION ETCHING-INDUCED DAMAGE IN INALAS INGAAS HETEROSTRUCTURES EVALUATED BY HALL MEASUREMENTS

The depth distribution of defects induced by reactive ion etching in InAlAs/InGaAs heterostructures has been determined from the measurements of low-temperature mobilities of samples with varying two-dimensional electron gas (2DEG) depth. The sample with a 2DEG depth of 35 nm from the surface showed no change in mobilities or sheet carrier densities, whereas the one with a 2DEG depth of 12.5 nm, etched under the same conditions using HBr plasma at a self-bias of -100 V, showed a large change in both mobilities and sheet carrier densities. The defect distribution, which was estimated using the reciprocal of mobilities, has been found to be exponential. A 1/e penetration depth of about 7.8 nm has been obtained for HBr plasma for self-bias voltages between -100 and -200 V and has been found to be independent of etching time. The exponential distribution of defects suggests that either ion channeling or diffusion is the possible mechanism of defect production in regions deeper than the projected ion range.