Pretreatment for surface leakage current reduction in type-II superlattice MWIR photodetectors

Abstract

Focal plane array based on InAs/GaSb type-II superlattice (T2SL) is expected as an alternative to HgCdTe. To get more competitive performance of T2SL detector, we need building up more reliable fabrication process. Especially, mesa formation and passivation with understanding of surface leakage mechanism is critical issue. Generally, the existence of dangling bonds at crystal surface or damaged layer and native oxides on etched mesa sidewall leads to surface leakage currents, which mostly degrade the detector performance. Many researchers adopted SiO2 film as an effective passivation layer, which was deposited by plasma enhanced chemical vapor deposition at low temperature. However, good passivation requires not only stable film, but also an effective surface treatment before passivation. There are few reports, which discuss the relation between treatment before passivation and device characteristics in T2SL photodetectors. In this work, we present dry etching mesa formation and the effect of pretreatment of passivation on T2SL p-i-n photodetector fabrication. We investigate R0A-Perimeter/Area relation and R0A temperature dependence with in-situ plasma treatment prior to the passivation. From results of electrical characterization and interface analysis using STEM, it is recognized that in-situ N2 plasma treatment was effective to surface leakage reduction.

Fabrication of 15-$\mu$ m Pitch $640\times512$ InAs/GaSb Type-II Superlattice Focal Plane Arrays

“…Although most of the research groups and developers prefer wet etch in mesa formation, a few of them use dry etching in mesa formation step [4]. Different types of gas mixtures are used in dry etching of InAs/GaSb T2SLs such as chlorine based [5], CH 4 based [6], and halogen gas mixtures [7]. For the formation of ohmic contact, Ti, Pt, and Au are used as ohmic contact metals by many groups [4], [8].…”