In-situ monolayer etching and regrowth of InP/InGaAsP

We have developed an etching process with real-time counting of each monolayer removed, thus achieving etching with monolayer precision and control. This is an exact reversal of the CBE process. The new etching capability which we refer to as monolayer chemical beam etching, CBET, is achieved by employing in-situ RHEED intensity oscillation monitoring during etch. Having both epitaxial growth and etching integrated in the same process and both capable of ultimate control down to the atomic layer precision represents a very powerful combination. This permits instant switching from growth to etching and vice versa, clean regrowth interfaces critical for device applications. The surface morphology is found to be dominated by the surface cation diffusion mechanism. With this understanding, novel methods that takes the advantage of enhanced migration of surface cations have been shown to greatly improve the surface morphology. We also show that CBET can be a very effective means of surface contaminant cleaning prior to regrowth. The effectiveness depends on the strength of chemical reactivity of the contaminant to form volatile chlorides. Using dielectric marks, selective-area etching and etching followed immediately by regrowth having excellent etched and regrown morphologies were obtained.