S. Arulkumaran

On the enhancement of effective barrier height in Tin-GaAs Schottky barrier diodes

Abstract Changes in the Current-Voltage (I-V) and Current-Voltage-Temperature (I-V-T) characteristics of Schottky Barrier Diodes (SBDs) on silicon doped n-GaAs ( Titanium n- GaAs ) after irradiation using protons at 100 keV with various doses (5 × 1013 to 1 × 1015 cm−2) are presented and analysed. Irradiated SBDs reverse leakage current is more compared to the un-irradiated SBDs. Heavily irradiated (1 × 1015 cm−2) SBDs almost behaves like an Ohmic contact at 360 K. The irradiated SBDs were annealed at two different temperatures (200 and 350°C for 15 min.) under nitrogen atmosphere and characterised using I-V and I-V-T measurements. Rectifying behaviour of the irradiated SBDs improves as the annealing temperature increases. Enhancement of the effective barrier height (Φe) and improvement in the ideality factor (n) has been observed in annealed (350°C for 15 min) proton irradiated Ti n- GaAs SBDs. This may be either due to hydrogen passivation of GaAs surface and/or removal of hydrogen related irradiation induced defects in SBDs. On the unirradiated and annealed (upto 350°C) there is no significant change in the characteristics as compared to the CONTROL SBDs.

Structural and mechanical properties of ion implanted GaAs and InP single crystals grown by the liquid encapsulated Czochralski technique

Abstract Ion implantation studies were carried out on liquid encapsulated Czochralski grown GaAs and InP single crystals. The hardness of samples irradiated at varying dosages was studied. The irradiated samples were characterized structurally by etching studies and electrically by I–V measurements. Double-crystal X-ray diffractometry was used to study the damage caused by ion implantation.

Electrical characteristics of 100 MeV 28Si implanted LEC grown GaAs〈100〉

Abstract Undoped semi-insulating gallium arsenide single crystals were grown in pBN crucible using LEC technique. 28Si implantation at various fluences was carried out using 100 MeV 28Si ion. Implanted samples were characterised using four probe and Hall measurements. In-situ resistance measurements were carried out for samples implanted with various fluences. The electrical characterisation results of 100 MeV 28Si implanted GaAs samples show an increase in mobility 5774 cm2/V.s (3800 cm2/V.s) and a decrease in sheet resistivity of the order of 2 × 10 2 Ω/q . The increase in mobility at 300 K may be due to better electrical homogeneity in the implanted layer, than in the virgin substrate. The implanted samples ( 100 MeV 1.5 × 10 13 cm −2 ) were annealed at different temperatures in the range of 200–400°C and characterised using Hall measurements at different temperatures (300–380 K). The implantation profile of the two buried layers by 100 MeV 1 × 10 12 cm −2 and 80 MeV 1 × 10 12 cm −2 for 28Si ion were observed and analysed using Scanning Electron Microscopy.

Annealing behaviour of 1 MeV hydrogen-implanted LEC grown InP

Abstract Hydrogen has been implanted in InP crystals at energy 1 MeV with fluence 1 × 1014 cm−2. Structural and electrical analyses were carried out on the implanted samples. Implanted samples have also been examined after furnace annealing. The microhardness of the implanted samples decreases with increase in annealing temperature. From Hall effect studies the carrier mobility of the implanted samples was found to decrease with increase in annealing temperature. The change in electrical behaviour is due to formation of a neutral complex involving hydrogen and the donor atom.

Effect of irradiation on the microhardness of the LEC grown semi-insulating GaAs single crystals

Abstract Undoped semi-insulating (SI) gallium arsenide (GaAs) single crystals were grown in the 〈100〉 direction by the liquid encapsulated Czochralski (LEC) technique. The grown crystals were cut and characterised by Hall effect measurement in the Van der Pauw configuration. Ion implantation has profound effects upon the elastic, mechanical, optical and structural properties of semi-conducting materials. The present study deals with the effect of ion implantation on microhardness of GaAs. Hydrogen ion implantation was carried out at room temperature on GaAs samples at 100 keV energy. Microhardness measurements were carried out after implantation and the change in the microhardness as a function of ion dose was evaluated. The irradiated samples were also characterised by using X-Ray diffraction (XRD) techniques.

Investigations on Au, Ag, and Al Schottky diodes on liquid encapsulated Czochralski grown n-GaAs(100)

The Schottky barrier heights of metals Au, Ag, and Al fabricated by vacuum vapor deposition on liquid encapsulated Czochralski (LEC) grown undoped ntype GaAs (n = 2.35 × 1015 cm−3) were measured with current-voltage (I-V) and capacitance-voltage (C-V) techniques. Good ohmic contacts were obtained through an after deposition anneal at 430°C for two minutes in an argon gas atmosphere. In the as-deposited state, Au, Ag, and Al gave very similar I-V characteristics for n-type substrates with the barrier height qϕb = 0.81-1.16 eV and ideality factor n = 1.02-1.15. The C-V measurement also gives the same value of barrier height. The distribution of carrier concentration along the radial distance of the wafer is of‘M’ shape. The Al/GaAs interfaces give the nonideal rectification behavior. The Au/GaAs interfaces give the near ideal rectification behavior. The barrier height of this interface is 0.89-0.92 eV and the ideality factor is about 1.10–1.19. Electron traps in the wafer have been found by constant capacitance deep level transient spectroscopy (CC-DLTS). Mainly the EL2, EL6, and EL3 (EI1) trap levels are prominent.

Current-voltage characteristics of low energy proton and alpha particle irradiated Au and Schottky barrier diodes

Abstract Experimental results on the considerable changes in the current-voltage (I–V) characteristics of proton and alpha particle (80 keV) irradiated and Schottky barrier diodes (SBDs) with different fluences are presented. The samples were irradiated at 300 K, after fabricating Au and Ag Schottky barrier diodes on the undoped liquid encapsulated Czochralski (LEC) grown n-GaAs (100) (3 × 1015cm−3). The parameter susceptible to this irradiation is the reverse leakage current of the SBDs. I–V characteristics were measured at different temperatures between 300 and 350 K. A correlation between change in reverse leakage current and incident particle fluence has been observed. The ideality factor and the series resistance of the diode increases with the increase of particle fluence. This may be due to the irradiation-induced defects which reduce the carrier lifetime and/or enhance the interface insulation region.

Investigations of the Electrical and Structural Characteristics of 50 MeV7Li Implanted SI-InP

Electrical characteristics of 50 MeV lithium (Li) ion implanted semi-insulating indium phosphide (SI-InP) have been investigated using resistivity and Hall measurements. The SI-InP samples were implanted with 50 MeV 7 Li ions of dose 1 x 10 14 and 5 x 10 15 cm -2 room temperature. In-situ resistance measurements were carried out on the SI-InP samples as a function of dose using fourprobe method. The resistance decreases as a function of dose. The sheet resistivity and Hall measurements were carried out on the as-implanted and annealed implanted samples using van der Pauw technique. In the as-implanted samples, the sheet resistivity decreases and the sheet carrier concentration increases with dose which indicates that 7 Li acts as a shallow interstitial donor. For the annealed implanted samples, the sheet resistivity increases and the sheet carrier concentration decreases. This may be due to the compensation of the implanted 7 Li and/or its interaction with defects in general displacing the 7 Li from its interstitial position with annealing. The cross-sectional SEM picture reveals the buried layer and the defects due to 7 Li implantation.

Investigations on the evaluation of schottky barrier diode parameters of the proton irradiated Ti/N-GaAs

Abstract An innovative approach has been made for the evaluation of Schottky barrier diode parameters namely, ideality factor (n), barrier height (O B) and series resistance (R s) from forward I—V characteristics. The ln(I) vs V plot for a diode in this region without the influence of the series resistance shows a linear part of the I—V characteristics. In this analysis, the Schottky barrier diode parameters have been extracted from the CONTROL (unirradiated), irradiated and annealed diodes. The major advantages of this method are the Schottky barrier diode parameters with high series resistance can be evaluated and the linear regression can be used for the entire bias range, which raise the accuracy of the results. The best fitted Schottky barrier diode parameters were calculated from the forward I—V characteristics, compared with the experimental results and discussed.