The effect of high-energy electron irradiation on ZnO-based ohmic and Schottky contacts

Abstract

A systematic study of radiation effects on the major parameters of ohmic and Schottky contacts based on n-ZnO is introduced. Al and Au metals were used as contact elements in order to fabricate the ohmic and Schottky structures, respectively. The transmission line method (TLM) measurements on Al/n-ZnO have revealed that high-energy (6, 9, 12 MeV) and relatively low-dose (3 × 10 12 e − cm −2 ) electron irradiation produced lower specific ohmic contact resistivity values as compared with the reference sample. The current-voltage (I-V ) and capacitance-voltage (C-V ) measurements on the Au/n-ZnO structures are shown to increase in ideality and to decrease in the Schottky barrier heights with increasing electron energy. These findings have been interpreted based on the assumption that the atoms of the contact elements diffused into the semiconductor material, thus turning the rectifying character to ohmic behaviour with the influence of radiation-matter interaction and subsequent annealing effects.

Long time stability of ITO/NiPc/ZnO/Al devices with ZnO buffer layer formed by atomic layer deposition technique–impedance spectroscopy analysis

“…The diagram, and also data from Ref. [18], indicates that Al forms a quazi-ohmic contact with ZnO. Therefore, the observed rectification takes place at the NiPc/ZnO heterojunction.…”

Electrical characterization of Au/n-ZnO Schottky contacts on n-Si

“…where˚b is the effective barrier height at zero bias, A* the Richardson constant which equals 0.15 A/cm 2 K 2 for n-ZnO [11,12], q the electron charge, V the forward-bias voltage, A the effective diode area, k the Boltzmann's constant, T the temperature in Kelvin and n is the ideality factor which is determined from the slope of the linear region of the forward bias ln I-V characteristic through the relation:…”

“…(3) has been found to be 1.21 and the rectification ratio is about 3 × 10 4 at 0.8 V. The value of the ideality factor is greater than unity. High values of n can be attributed to the presence of the interfacial thin native oxide layer at Au and ZnO interface, a wide distribution of low-Schottky barrier height (SBH) patches (or barrier inhomogeneities), to the series resistance effect and to the bias voltage dependence of the SBH [11]. I 0 is determined from the intercept of ln I vs. V curve on the y-axis.…”

Radiation effects on ohmic and Schottky contacts based on 4H and 6H-SiC

“…After each irradiation step, the TLM measurements were repeated. The details of TLM measurements and a SEM image of the shadow mask used in transferring the ladder pattern to the sample surface can be found in our earlier reports [21,22]. In order to perform I-V and C-V measurements Keithley-487 picoampermeter and HP-4192 A impedance analyzer (at 50 kHz) were used, respectively.…”