Chemical Etching of (001) InP by HBr ‐ H 2 O 2 ‐ H 2 O ‐ HCl Solution

We developed a new etchant system based on , , , and for (001) wafers. We discovered that and have different reactivities with different {111} planes of . Etching behavior of our new etchant system was shown to depend on the relative concentration of and . Etchants with a low concentration were more reactive with the {111} B planes and led to elongated pits with their long axis parallel to the <110> direction. Etchants with a high concentration were more reactive with the {111} A planes and the long axis of the resultant elongated pits was parallel to the <110> direction. We selected an optimal etchant formulation to fabricate mesa structures with smooth (non‐reentrant) walls in 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.