Mesa etching process for InAs/GaSb SLs grown by MBE

Dry etching and wet etching were usually used in the mesa etching process of InAs/GaSb SLs. Three kinds of etch atmosphere(Cl2 based, Ar based and CH4 based)were studied in inductively coupled plasma(ICP) dry etching. The results show that the CH4 based atmosphere give much more smooth surface and less etch pits according to the SEM measurement. Then wet etching was introduced to eliminate the etching damage of ICP dry etching, tartaric acid based etchant and phosphoric acid based etchant, were studied. It was found that the phosphoric acid based etchant gave better result to remove etching damage, and provide a more stable etching rate. InAs/GaSb SLs photodiodes by standard photolithographic procedures were fabricated using this etching recipe. The diodes exhibits a high breakdown voltage and low leakage current, the measurement result reveals a dynamic impedance values of R0A =1.98104 cm2 at 77 K.