R. R. Sumathi

Investigations on Al/BaTiO3/GaN MFS structures

Abstract A metal–insulator–semiconductor (MIS) device structure has been established on GaN by using BaTiO 3 , a ferroelectric material, as an insulating layer. The composition of the deposited ferroelectric layers was studied using X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) analysis. Fabricated Al/BaTiO 3 /GaN metal–ferroelectric–semiconductor (MFS) structures have been characterised through capacitance–voltage ( C – V ) measurements. Improved C – V characteristics have been observed in comparison to other traditional oxide insulators. An inversion of GaN MFS structures has been attained just for the applied voltage of 5 V due to the high dielectric constant and large polarisation field of the gate ferroelectric layer. The bias stress measurements indicate a high stability of the ferroelectric material over a period of 10 4 s.

Investigations on the CdS passivated anodic oxide–InP interface for MOS structures

Abstract Thin layers of cadmium sulfide have been deposited on 〈111〉 n-InP using the chemical bath deposition technique at room temperature. X-ray photoelectron spectroscopy (XPS) results show that sulfur in CdS removes native oxide present on the InP surface and forms a chemically stable surface. Anodic oxidation was carried out on the CdS passivated InP surface. XPS results of oxides show the formation of highly stable P2O5. Improved C–V characteristics have been observed on CdS treated MOS diodes. Delay time measurements and bias stress measurements demonstrate the high stability of CdS passivated MOS diodes. NSS values as low as 3×1010 cm−2 eV−1 were obtained for CdS treated MOS diodes.

BaTiO3 as an insulating layer for InP-based metal-insulator-semiconductor structures

Abstract Barium titanate (BaTiO 3 ) films were successfully deposited on InP substrates using sol–gel process. The composition of the film has been analysed using X-ray photoelectron spectroscopy (XPS) and the formation of BaTiO 3 has been confirmed. Capacitance–voltage ( C – V ) measurements were carried out on the fabricated Au/BaTiO 3 /InP MIS structures. The surface state density ( N SS ) values were calculated from the C – V measurements using Termans analysis and the minimum N SS value calculated is 7×10 10 cm −2 eV −1 . Deep-level transient spectroscopic (DLTS) measurements have also been carried out on the fabricated MIS structures to find out the traps at the interface. Only one interface state trap is observed at 0.55 eV for Au/BaTiO 3 /InP MIS structures.

Deep Level Transient Spectroscopic Analysis on Au/SiO2/InP MOS Structures

Deep Level Transient Spectroscopy (DLTS) studies have been carried out on Au/SiO 2 /InP Metal-Oxide-Semiconductor (MOS) diodes. Majority and minority carrier traps have been observed for the room temperature SiO 2 deposited samples, The effect of substrate temperature during SiO 2 deposition has been analysed using DLTS. It has been observed that the minority carrier trap is removed while SiO 2 deposition is carried out at an elevated temperature. The detected traps have been analysed under different reverse bias values to distinguish between the bulk and interface traps.

A new etchant to reveal the subsurface damage on polished gallium arsenide substrates

Abstract In the present investigations, a new etchant, viz., Bi(NO 3 ) 3 H 2 O 2 HCI (“BNCL etchant”) has been established for GaAs to reveal the subsurface damage induced during the polishing procedures. The investigated (1 0 0) oriented, silicon-doped n-type GaAs and undoped semi-insulating GaAs wafers were polished with slurries having pH 8 and 9. After etching, the shallow scratches are visible in addition to the wave-like defects. The etching rate was 6.5 μm/min for n-type and 8 μm/min for semi-insulating. When the etching was carried out for 2 min, all the observed damage vanished and most of the surface of both (n-type and semi-insulating) samples were found to be uniformly etched. The capability of the etchant to reveal the subsurface damage has been confirmed.