Reactive ion etching for mesa structuring in HgCdTe

Abstract

Both wet chemical and dry plasma etching techniques have been investigated for mesa structuring in n- and p-type HgCdTe. Scanning electron microscopy (SEM) confirms the isotropic nature of a bromine-based wet chemical etching solution, and the anisotropic profile that results from reactive ion etching. Laser-beam-induced-current (LBIC) measurements reveal no significant modifications to the electrical properties for chemically etched HgCdTe material, but clearly demonstrate a p- to n-type conversion in p-type samples and n+ doping in n-type samples for reactive ion etching (RIE) (processing conditions: 400 mTorr, CH4/5H2, 0.4 W/cm2). LBIC measurements following low-temperature (200 °C) mercury annealing of RIE-processed samples indicate the full restoration of electrical properties to that of the initial as-grown wafers, thus preserving the beneficial aspects of RIE for anisotropic mesa structuring in HgCdTe.

Etching of mesa structures in HgCdTe

“…[1][2][3] Though some success has been reported in this direction, these etching processes induce lateral damage and alter the electrical and photo-electrical properties of HgCdTe layers. [4][5][6] The damages induced in the HgCdTe layers during dry etching can cause undesirable type conversion of the layer being etched or can create mobile defects, 7,8 thus causing thermal and temporal instability in the devices. The induced surface roughness forms high surface recombination surfaces/ regions.…”

Wet Etching of HgCdTe in Aqueous Bromine Solutions: a Quantitative Chemical Approach

“…The damage induced in the HgCdTe during dry etching can convert n-type HgCdTe layers to p-type or create mobile defects. [1][2][3][4] To fabricate a defect-free surface or to renew an altered surface, wet etching techniques can be employed. Current understanding of the phenomena that govern these techniques remains mainly empirical.…”

Low-energy electron-enhanced etching of HgCdTe

“…Unfortunately, the high-energy ion bombardment involved in the RIE process creates damage sites in the HgCdTe material, which causes type conversion, among other problems. [1][2][3] The ion energy can be reduced by using electron cyclotron resonance (ECR) plasma etching; however, the etched surfaces are not reliably stoichiometric or smooth. [4][5][6] We have been exploring a new dry-etching technique called low-energy electron-enhanced etching (LE4) with the objectives of achieving low-damage, smooth, stoichiometric etched surfaces of HgCdTe with high-resolution pattern transfer.…”