D. N. Bose

Gd2O3, Ga2O3(Gd2O3), Y2O3, and Ga2O3, as high-k gate dielectrics on SiGe: A comparative study

In this paper we report a comparative study of the electrical properties of some oxides e.g. Gd 2 O 3 , Ga 2 O 3 (Gd 2 O 3 ), Y 2 O 3 and Ga 2 O 3 as gate dielectric for strained Si 0.74 Ge 0.26 MOS devices. The deposited films have been characterized using EDAX, SIMS and ellipsometry. The Au / oxide / SiGe MIS structures using these insulators were examined using I-V, C-V and G-V techniques. Though Gd 2 O 3 and Y 2 O 3 showed highest resistivity and breakdown strength, Ga 2 O 3 (Gd 2 O 3 ) was found to be most effective for surface passivation of SiGe giving lowest interface state density while pure Ga 2 O 3 was incapable of passivating SiGe surface.

Capacitance–voltage measurements on plasma enhanced chemical vapor deposited silicon nitride films

Silicon nitride films of varying composition have been deposited with nitrogen dilution onto p-type silicon substrates at 250 °C by plasma enhanced chemical vapor deposition technique. Careful and detailed capacitance–voltage (C–V) measurements have been undertaken in the metal-insulator-semiconductor configuration. Silicon-rich films are found to exhibit large symmetric hysteresis loops in the C–V curve while the nitrogen-rich films display much smaller asymmetric hysteresis loops. Furthermore, the minimum interface state density is observed to decrease with the increase in nitrogen to silicon ratio. In this study we have observed that the concentration of both electron as well as hole traps are much lower for the nitrogen-rich films.

Plasma enhanced growth, composition and refractive index of silicon oxynitride films

Abstract Silicon oxynitride films of various compositions have been prepared by the glow discharge decomposition of silane (SiH 4 ) and nitrous oxide (N 2 O). The refractive index of the films has been measured using ellipsometry, while the composition of the films has been determined using Rutherford backscattering (RBS) and elastic backscattering (EBS) techniques. This study has demonstrated that the measurement of composition using EBS technique is distinctly superior to RBS technique, particularly for the films like silicon oxynitride containing multicomponent light elements in low concentration.

XPS investigation of CdTe surfaces: effect of Ru modification

The composition of n- and p-type CdTe surfaces before and after chemical modification by Ru have been examined using X-ray photoelectron spectroscopy (XPS). While the chemically etched unmodified surfaces were found to be covered by a thin layer of oxide due to ambient oxidation of a Te layer, Ru-modified surfaces were found to have a thicker oxide layer of composition TeOx where x=1.97 and 2.07 for p- and n-CdTe respectively. The Cd:Te ratios of the surfaces were determined from the peak intensities and showed depletion of Cd due to modification. These results can be related to the increase in band-bending at the surface due to Ru modification and the increase in minority carrier diffusion lengths on both p- and n-CdTe.

Grain size dependence of mobility in polycrystalline n‐indium phosphide

Polycrystalline n‐indium phosphide (InP) with grain sizes varying from 15 to 2000 μm has been prepared by iodine chemical reaction and synthesis solute diffusion (SSD) techniques. The variation of electron mobility and hence electron mean free path with grain size has been determined from conductivity and Hall effect studies, taking into account the effect of compensation as discussed by Jensen. The results show that electron mobility at 300 K increases from 29 to 691 cm2/V s with grain sizes increasing from 15 to 2000 μm. While for a single crystal the electron mobility varied with temperature between 160–300 K as T−2.25, for polycrystalline InP the variation was T−2.44 (2000 μm in grain size) and T−2.97 (200 μm in grain size) showing the effect of grain boundary scattering. The impurity activation energies have also been determined and were found to increase with a decrease of grain size.

Improved Schottky barrier on n-InP by surface modification

Abstract Modification of the surface of InP by ruthenium treatment increases the Schottky barrier height of Ag/n-InP junctions from 0.58 to 0.75 eV. The ideality factor n is found to decrease from 2.06 to 1.20, J0 from 4.8 × 10−6 to 1.47 × 10−7 A/cm2 and A ∗∗ from 22.2 to 8.6 A cm−2 K−2.

Effect of ammonia plasma pretreatment on the plasma enhanced chemical vapor deposited silicon nitride films

Abstract Silicon-rich, nearly stoichiometric and nitrogen-rich silicon nitride films have been prepared by the glow-discharge decomposition of silane and ammonia with nitrogen dilution, with and without ammonia plasma pre-treatment of the silicon substrate. A considerable improvement in the silicon nitride/silicon interface, as evident from the large reduction in the minimum interface state density (Dit)min, due to ammonia plasma pretreatment is observed.

Improved surface properties of InP through chemical treatments

Chemical treatment is a very effective method for passivation of semiconductor surfaces. HF and sulfide (Na2S⋅9H2O) pretreatments of InP have been shown to improve the properties of BaF2/InP interface significantly. The interface state density as obtained from C–V (1 MHz) measurements of metal‐insulator–semiconductor structures was found to be reduced from 5.8×1010 cm−2 eV−1 to 2.1×1010 cm−2 eV−1 after HF treatment. The reduced interface state density resulted in increased photoluminescence intensity. X‐ray photoelectron spectroscopy studies revealed that the formation of InF3 and P2S3 after HF and sulfide treatments, respectively, are responsible for better interfacial behavior.

Electrical conduction studies of plasma enhanced chemical vapor deposited silicon nitride films

Current conduction mechanisms have been studied for three representative films, namely, silicon-rich, nearly stoichiometric and nitrogen-rich silicon nitride films, prepared by rf glow-discharge decomposition of silane and ammonia with nitrogen dilution. Ohmic conduction has been observed for all the films at low electric fields. The dominance of Poole–Frenkel conduction at intermediate fields and Fowler–Nordheim conduction at high fields has been observed both for the nitrogen-rich and the nearly stoichiometric films. However, for the silicon-rich films, the Poole–Frenkel conduction mechanism dominates both for the intermediate as well as the higher fields. This study indicates that the silicon-rich films have the highest density of traps and the nitrogen-rich films have the lowest, which may be ascribed to the effect of nitrogen dilution.

Pulsed laser deposition of ZnTe thin films

Abstract Thin films of ZnTe were deposited on glass and Si by pulsed laser ablation at substrate temperatures of 26 °C and 286 °C. X-ray diffraction studies showed that films deposited at 26 °C were amorphous and those deposited at 286 °C were polycrystalline. X-ray photoelectron spectroscopy (XPS) showed the Zn: Te ratio to be 49.1: 50.9 for both types of films. The band gap of the films deposited at 286 °C was 2.2 eV. The conductivity of the films was 1.09 × 10 −3 Ω −1 cm −1 and 2.59 × 10 −6 Ω −1 cm −1 respectively at 300 K. The variation of conductivity with temperature and the properties of ZnTe/Si heterojunctions were also studied.