Surface passivation of HgCdTe by CdZnTe and its characteristics

Abstract

In this paper, we report the results of capacitance-voltage measurements conducted on several metal-insulator semiconductor (MIS) capacitors in which HgCdTe surfaces are treated with various surface etching and oxidation processes. CdZnTe passivation layers were deposited on HgCdTe surfaces by thermal evaporation after the surfaces were etched with 0.5-2.0% bromine in methanol solution, or thin oxide layers (to~ -few ten A) were grown on the surfaces, in order to investigate effects of the surface treatments on the electrical properties of the surfaces, as determined from capacitance-voltage (C-V) measurements at 80K and 1 MHz. A negative flat band voltage has been observed for MIS capacitors fabricated after etching of HgCdTe surfaces with bromine in methanol solutions, which is reported to make the surface Te-rich. It is inferred that residual Te on the surface is a positive charge, Te% C-V characteristics for MIS capacitors fabricated on oxide surfaces grown by air-exposure and electrolytic process have shown large hysteresis effects, from which it is inferred that imperfect and electrically active oxide compounds and HgTe particles near the surface become slow interface states.

Investigation of passivation processes for HgCdTe/CdS structure for infrared application

“…The maximum fast surface state density per unit energy so measured was 1.5 Â 10 15 eV À 1 m À 2 at the edge of the band gap. This value also compares favorably with the best values reported by others [6,14]. The frequency-dependent C -V characteristics of our devices are being analysed and will be published separately.…”

“…The rms roughness also increased from 1 nm to 1.4 nm. It is well known that the surface of HgCdTe is rendered rich in elemental tellurium following etching with Br-MeOH [14]. The bright particles seen in Fig.…”

Effects of bulk and surface conductivity on the performance of CdZnTe pixel detectors

“…Our results, which we present below, support this general idea [14][15][16][17] that the Te layer is formed during the fabrication process, which later becomes partially or completely oxidized after the passivation step, or as a result of natural oxidation in air. The later process starts as soon as the surface of CZT is exposed to air or to the oxygen outgasing in the sputtering chamber.…”

Metal-Insulator-Semiconductor Photodetectors

“…Some subsequent research focused on the investigation of passivation in the HgCdTe MIS structures since the effective passivation of surface states could reduce the dark currents as well. For example, passivation by CdZnTe was investigated by Lee et al [ 71 ], and ammonium sulfide was used to improve the interface of common metal/ZnS/HgCdTe MIS structures [ 72 ]. In [ 71 ], bromine etching or intentional oxidation of HgCdTe was performed before the deposition of CdZnTe on HgCdTe, to investigate the corresponding properties of passivation.…”

“…For example, passivation by CdZnTe was investigated by Lee et al [ 71 ], and ammonium sulfide was used to improve the interface of common metal/ZnS/HgCdTe MIS structures [ 72 ]. In [ 71 ], bromine etching or intentional oxidation of HgCdTe was performed before the deposition of CdZnTe on HgCdTe, to investigate the corresponding properties of passivation. Fixed charges, slow and fast interface states were desired to be minimized to avoid the degradation of the HgCdTe detector performance.…”