Highly uniform N-InAlAs/InGaAs HEMT´s on a 3-in InP substrate using photochemical selective dry recess etching

Large-area photochemical selective dry etching has been developed for use in InGaAs/InAlAs heterojunction fabrication involving CH/sub 3/Br gas and a low-pressure mercury lamp. The etch rate of the InGaAs layer was 17 nm/min and the etch ratio of InGaAs to InAlAs was around 25 to 1. The dry recess was performed for N-InAlAs/InGaAs HEMT´s on a 3-in wafer using photochemical etching. The standard deviation of the threshold voltage across the wafer was 18 mV at a threshold voltage of -0.95 V, and the transconductance of 456 mS/mm was obtained for a 1.1- mu m-long gate within a standard deviation of 14.9 mS/mm.<>