Chemical Etching of (001) InP by HBr-H sub 2 O sub 2 -H sub 2 O-HCI Solution.

We developed a new etchant system based on HBr, H sub 2 O sub 2, HCI and H sub 2 O for (001) InP wafers. We discovered that HCI and HBr have different reactivities with different {111} planes of InP. Etching behavior of our new etchant system was shown to depend on the relative concentration of HCI and HBr. Etchants with a low HBr concentration was more reactive was more reactive with the {111} A planes and it led to elongated pits with their long axis parallel to the direction. Etchants with a high HBr concentration was more reactive with the {111} A planes and the long axis of the resultant elongated pits was parallel to the direction. We selected an optimal etchant formulation to fabricate mesa structures with verticals walls in InGaAs/InP wafers leading to a precise width control of the active layers in Mesa Buried Heterostructure Lasers. Our ability to etch vertical planes was also important for mirror fabrication in integrated optical devices.