K. Ejderha

Capacitance–conductance characteristics of Au/Ti/Al2O3/n-GaAs structures with very thin Al2O3 interfacial layer

High-k Al2O3 with metallic oxide thickness of about 3 nm on n-type GaAs substrate has been deposited by the atomic layer deposition (ALD) technique. Thus, it has been formed the Au-Ti/Al2O3/n-GaAs MIS structures. It has been seen that the MIS structure exhibits excellent capacitance-voltage (C–V) and current-voltage (I–V) properties at 300 K. The saturation current of the forward bias and reverse bias I–V characteristics was the same value. An ideality factor value of 1.10 has been obtained from the forward bias I–V characteristics. The C–V characteristics of the structure have shown almost no hysteresis from +3 V to −10 V with frequency as a parameter. The reverse bias C–V curves have exhibited a behavior without frequency dispersion and almost hysteresis at each frequency from 10 kHz to 1000 kHz.

Effect of temperature on the current (capacitance and conductance)–voltage characteristics of Ti/n-GaAs diode

In this study, Ti/n-GaAs Schottky barrier diode has been fabricated by DC magnetron sputtering. The current–voltage, capacitance–voltage, and conductance–voltage characteristics of Ti/n–GaAs diode have been investigated in the temperature range of 80–320 K. The ideality factor and barrier height values have been calculated from the forward current–voltage characteristics. The variation of the diode parameters with the sample temperature has been attributed to the presence of the lateral inhomogeneities of the barrier height. The temperature dependent capacitance–voltage characteristics have been measured to calculate the carrier concentration, diffusion potential, barrier height, and temperature coefficient of the barrier height (α = −0.65 meV K−1). The fact that the temperature coefficient of the barrier height changes from metal to metal has been ascribed to the chemical nature of the contact metal or metal electronegativity.

The Characteristic Parameters of Ni/n-6H-SiC Devices Over a Wide Measurement Temperature Range

Ni/n-type 6H-SiC/Ni Schottky barrier diodes (SBDs) have been prepared by the DC magnetron sputtering deposition technique. Their current-voltage characteristics (I-V) have been measured in the measurement temperature range of 40-400 K with steps of 20 K under dark conditions. The barrier height (BH) values from the temperature-dependent forward and reverse bias I-V characteristics by different methods coincide with each other which indicates the elimination of the polarity between the Si and C ions. The ideality factor value remains almost unchanged in the 160-400 K range, and below 160 K, it has the values of 1.57 at 140 K, and 3.82 at 60 K. The BH has the values of 0.79 eV at 400 K, and 0.71 eV at 300 K. The decrease in the BH is due to the fact that the current will preferentially flow through the lowest BH with decreasing temperature due to barrier inhomogeneity. The value of 0.71 eV at 300 K is in close agreement with the values of 0.65 and 0.83 eV reported from the forward bias I-V characteristics for the Ni /n-type 6H-SiC in the literature. Thus, it has been concluded that the reduced barrier devices are promising for applications in devices operating at cryogenic temperatures as infrared detectors, sensors in thermal imaging and small signal zero-bias rectifiers and microwave mixers.

THE CHARACTERISTIC DIODE PARAMETERS IN Ti/p-InP CONTACTS PREPARED BY DC SPUTTERING AND EVAPORATION PROCESSES OVER A WIDE MEASUREMENT TEMPERATURE

The titanium/p-indium phosphide (Ti/p-InP) Schottky diodes (SDs) have been prepared by thermal evaporation and DC magnetron sputtering deposition. Then, their current–voltage (I–V) characteristics have been measured in the sample temperature range of 100–400K with steps of 20K. The characteristic parameters of both Ti/p-InP SDs have been compared with each other. The barrier height (BH) values of 0.824 and 0.847 at 300K have been obtained for the sputtered and the evaporated SDs, respectively. This low BH value for the sputtered SD has been attributed to some defects introduced by the sputtered deposition technique over a limited depth in to the p-type substrate. The BH of the evaporated and sputtered diodes has decreased with the standard deviations of 58 and 64mV obeying to double-Gaussian distribution (GD) in 220–400K range, respectively, and it has seen a more sharper reduction for the BHs with the standard deviations of 93 and 106 mV in 100–220K range. The Richardson constant values of 89.72 and 53.24A(Kcm)−2 (in 220–400K range) for the evaporated and sputtered samples, respectively, were calculated from the modified ln(I0/T2)−q2σs2/2k2T2 vs (kT)−1 curves by GD of the BHs. The value 53.24A(Kcm)−2 for the sputtered sample in high temperatures range is almost the same as the known Richardson constant value of 60A(Kcm)−2 for p-type InP.

Characteristic diode parameters in thermally annealed Ni/p-InP contacts

The Ni/p-InP Schottky diodes (SDs) have been prepared by DC magnetron sputtering deposition. After the diode fabrication, they have been thermally annealed at 700℃ for 1 min in N 2 atmosphere. Then, the current-voltage characteristics of the annealed and non-annealed (as-deposited) SDs have been measured in the measurement temperature range of 60-400 K with steps of 20 K under dark conditions. After 700℃ annealing, an improvement in the ideality factor value has been observed from 60 to 200 K and the barrier height (BH) value approximately has remained unchanged in the measurement temperature range of 200-400 K. The BH of the annealed diode has decreased obeying the double-Gaussian distribution (GD) of the BHs with decreasing measurement temperature from 200 to 60 K. The BH for the as-deposited diode has decreased with decreasing temperature obeying the single-GD over the whole measurement temperature range. An effective Richardson constant value of 54.21 A/cm 2 K 2 for the as-deposited SD has been obtained from the modified Richardson plot by the single-GD plot, which is in very close agreement with the value of 60 A/K 2 cm 2 for p-type InP. The series resistance value of the annealed SD is lower than that of the non-annealed SD at each temperature and approximately has remained unchanged from 140 to 240 K. Thus, it can be said that an improvement in the diode parameters has been observed due to the thermal annealing at 700℃ for 1 min in N 2 atmosphere.