Effect of annealing on electrical properties of radio-frequency-sputtered ZnO films

Abstract

We report on the electrical properties of ZnO films and devices grown on different substrates by radio-frequency magnetron sputtering. The films grown on c-plane sapphire were annealed in the range 800-1,000°C. The electron concentration increased with annealing temperature reaching 1.4 3 10 19 cm -3 for 1,000°C. Mobility also increased, however, reaching its maximum value 64.4 cm 2 /V Á sec for 950°C anneal. High-performance Schottky diodes were fabricated on ZnO films grown on n-type 6H-SiC by depositing Au/Ni(300/300 Å ). After annealing at 900°C, the leakage current (at -5 V reverse bias) decreased from 2.2 3 10 ÿ7 A to ;5.0 3 10 ÿ8 A after annealing at 900°C, the forward current increased by a factor of 2, and the ideality factor decreased from 1.5 to 1.03. The ZnO films were also grown on p-type 6H-SiC, and n-ZnO/p-SiC heterostructure diodes were fabricated. The p-n diode performance increased dramatically after annealing at 950°C. The leakage current decreased from 2.0 3 10 ÿ4 A to 3.0 3 10 ÿ7 A at -10 V reverse bias, and the forward current increased slightly from 2.7 mA to 3.9 mA at 7 V forward bias; the ideality factor of the annealed diode was estimated as 2.2, while that for the as-grown sample was considerably higher.

Analysis of Schottky Contact Formation in Coplanar Au/ZnO/Al Nanogap Radio Frequency Diodes Processed from Solution at Low Temperature

“…We note that the current rectification ratio values achieved here exceed even those of ZnO Schottky diodes fabricated via vacuum-based techniques such as molecular beam epitaxy (MBE) and sputtering, for which typically values fall in the range of 10 3 –10 4 − with the highest current rectification ratio of ∼10 5 reported for high-temperature-annealed sputtered ZnO Schottky diodes . Only devices fabricated on bulk single-crystal ZnO or on high-quality ZnO layers grown using pulsed laser deposition (PLD), demonstrate superior current rectification.…”

“…We note that the current rectification ratio values achieved here exceed even those of ZnO Schottky diodes fabricated via vacuum-based techniques such as molecular beam epitaxy (MBE) and sputtering, for which typically values fall in the range of 10 3 −10 431−35 with the highest current rectification ratio of ∼10 5 reported for high-temperature-annealed sputtered ZnO Schottky diodes. 36 Only devices fabricated on bulk singlecrystal ZnO or on high-quality ZnO layers grown using pulsed laser deposition (PLD), demonstrate superior current rectification. For example, Nakano et al 37 fabricated poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PE-DOT:PSS) Schottky contacts on 0001 single-crystal ZnO with rectification ratios of 10 9 at ±2 V. Similarly, Allen et al 38 achieved current rectification values of up to 10 9 by depositing silver oxide Schottky contacts on the Zn polar surface of ZnO wafers, while Muller et al 39 reported a maximum rectification ratio value of 7 × 10 10 for Schottky diodes based on PLDgrown ZnO and sputtered PdOx contact.…”

Effect of annealing temperature on structural, electrical, and UV sensingcharacteristics of n-ZnO/p-Si heterojunction photodiodes

“…A wide-bandgap n-type semiconductor ( ∼3. 1-3.4 eV) zinc oxide (ZnO) is an attractive material due to some important features such as good electrical and optical behaviors, direct band gap, and large exciton binding energy (60 meV) [1][2][3]. These features make ZnO an important material for optoelectronic applications, particularly in ultraviolet (UV) sensing applications [4][5][6].…”