Characteristics of InAs QDs/GaAs RC-SACM APD on the Etching Process of the Active-Mesa

The dependence of dark current (ID) on the etching process of active-mesa is investigated in two types of InAs quantum dots/GaAs resonant-cavity separate absorption, charge and multiplication avalanche photodiode (InAs QDs/GaAs RC SACM APD), one with inductively coupled plasma (ICP) etched active-mesa and the other with chemically wet etched structure. For both two types, the dark current is originated by the surface, eliminating the bulk properties including gain effect as major source. However, the dark current shows clearly different behaviors due to only active-mesa etching methods. The dark current in dry-etched type is dominated by a surface recombination-generation (R-G) current without surface tunneling current. On the other hand, in wet-etched type the surface tunneling current is a dominant component of the dark current, which exponentially increases and is strongly dependent on the bias. These results are attributed by a different electric field strength adjacent to surface, resulting from different etch-profiles.