Vesna Damnjanović

Photo-electric characteristics of HgCdTe tunnel MIS photo-detectors

The photo-electric characteristics of tunnel MIS photo-detectors based on Hg1−xCdxTe for x ≈ 0.2 are presented. In order to reduce or eliminate Fermi level pinning, a passivation dielectric layer with thickness allowing for free carrier tunneling was grown on the metal–semiconductor interface. Dielectric layers composed of native oxides, native fluorides, SiO2 or Al2O3 were investigated. Values as high as 6.2 A W−1 for spectral responsivity and 5.3 × 1010 cm Hz1/2 W−1 for specific detectivity were obtained.

Electrical characteristics of HgCdTe Schottky diode photo-detectors with passivation layers transparent to free carriers

The characterization and fabrication of Schottky diodes based on Hg1−xCdxTe for x ≈ 0.2 are presented. In order to reduce or eliminate Fermi level pinning a passivation dielectric layer was specially grown on the metal–semiconductor interface. Its thickness had to be reduced to allow for free carrier tunnelling. Dielectric layers composed of native oxides, native fluorides, SiO2 or Al2O3 were investigated. Interface trap density of less than 3 × 1011 cm−2 eV−1 and interfacial layer charges of less than 1 × 1011 cm−2 were obtained. Diode characterization was performed by analysing I/V characteristics. The barrier heights for different metals, penetration coefficient for free carrier tunnelling through the dielectric potential barrier and diode ideality factor for different dielectric layer thicknesses were estimated. The barrier height showed pronounced dependence on the metal applied. The best results for an ideality factor of 1.5 were achieved with the Schottky diode samples passivated with native fluoride, the values for other dielectrics being smaller than 3. High values for diode differential resistance were obtained.

CHARACTERIZATION OF PERIODIC CYLINDRICAL SUBSURFACE DEFECTS BY PULSED FLASH THERMOGRAPHY

A characterization of cylindrical periodic subsurface defects of different sizes by means of pulsed thermography is presented in the paper. To ensure a uniform thermal flux distribution, the test samples were heated in lab conditions using two photographic flashes. Surface temperature was intentionally recorded at an angle to the normal of the sample surface. Recorded temperatures were compared with simulated temperatures and the differences in temperature peak values and temperature peak positions were noted. The thermal image was transformed based on known positions of four noncollinear points, in order to cancel out errors resulting from image recording at an angle. The uniformity of surface heating and the effect of the positions of the defects on the results were tested by means of a simulation model. The positions did not affect defect characterization. It was also found that in spite of nonuniform heating, if the reference points were selected properly, the difference in temperature contrast was negligible.

Investigation of dielectric — Semiconductor interface in MIS structures based on p-Hg 0.8 Cd 0.2 Te

In this paper we describes technological processes for the stabilization of interface between p-Hg_1-xCd_x and dielectric. Native oxide and native fluoride, as well as Al₂O₃ and SiO₂, have been applied as dielectrics. Influence of technological parameters used in dielectric layers production on interface charge densities was studied. Characterization of the produced structures has been carried out by analyzing their C/V diagrams. Based on the characterization results, the choice of the most suitable values of technological parameters for each dielectric has been made, thus enabling achievement of low values of the interface charges density. Produced tunnel MIS photo detectors show clearly exhibited dependence of Schottky barrier height on the metal used and specific detectivity as high as 5 × 10¹⁰ cm·Hz^1/2W^-1.

Production and characterization of cadmium-mercury-telluride photodiodes in 1.5-3.5 /spl mu/m spectral range

Photodiodes based on p-type monocrystal Cd/sub x/Hg/sub 1-x/Te, with composition x between 0.3 and 0.5 suitable for the spectral range 1.5-3.5 /spl mu/m, are produced. There are two methods of formation of the p-n junction: diffusion in mercury vapor and implantation by aluminum ions. Produced photodiodes have been tested for the following parameters: relative spectral response, current response, detectivity and response time.