Reactive ion etching-induced damage in InAlAs/InGaAs heterostructures

Due to the advances in lithography and dry processing technologies it is now possible to fabricate devices with lateral dimensions in the nanometer range. Dry processes such as reactive ion etching (RIE) or chemically assisted ion beam etching (CAIBE), are generally required to provide the etch anisotropy needed to define such small structures. Unfortunately, the energetic ions in these ion beam processes introduce crystal damage which results in deterioration of electronic and optoelectronic properties of the semiconductor material. In order to exploit the full potential of the dry processes it is very important to characterize and understand the process-induced damage. This is particularly true in III-V semiconductor structures, where thermal annealing is often ineffective for restoring crystalline order. At present, the mechanism of damage introduction during dry etch processes is not clearly understood. The damage extends well beyond the calculated projected ion ranges. In addition, in RIE the energy and the flux of ions bombarding the etched wafer can only be controlled indirectly by adjusting the rf power, the pressure etc. Unless special techniques are used to measure the ion energy distribution, only the maximum possible ion energy is known from the value of the self-bias voltage. Also, in most situations the nature of the ions, their fluxes or the ion/neutral ratio are unknown. This lack of information further complicates the prediction of the extent of damage. Thus, the significance of characterization of dry etch induced damage in the fabrication of devices cannot be overemphasized. In this paper, we report the study of RIE-induced damage in the InAlAs/InGaAs material system which has great potential for applications in microwave devices and long-wavelength optical communications due to its excellent transport properties