Table 2.

ZnO-based p-n heterojunction photodiodes.

Device structure	Fabrication Method	Electrodes	Detecting range	Forward threshold voltage	Dark current	Responsivity	Response time	Ref.
ZnO/NiO:Li	PLD	Au; ITO	UV	1 V	____	0.3 A/W at −6 V bias (360 nm)	____	[53,54]
p-NiO/ i-ZnO/n-ITO	e-beam evaporation	____	UV	1 V	10 nA/cm2 (−5 V)	____	____	[55]
n-ITO/ i-ZnO/ p-NiO				2 V	100 nA/cm2 (−5 V)
n-ZnO/p-SiC	MBE	Au/Al; Au/Ni	UV	5 V	2×10−4 A/cm2 (−10 V)	0.045 A/W at −7.5 V bias	____	[56]
n-ZnO/p-Si	RF Sputtering	Au/Al; In	UV/Visible	____	____	0.5 A/W (310 nm) and 0.3 A/W (650–nm) at −30 V bias	____	[57]
n-ZnO/p-Si	sol-gel	Au	UV/Visible	1 V	7.6×10−5 A/cm2 (−5 V)	____	____	[58]
n-ZnO/p-Si	RF Sputtering	In; Cu	UV/Visible	____	∼10−4 − 10−3 A/cm2 (−5 V)	0.14–0.29 A/W at −5 V bias	35 ns	[59,60]
ZnO:Al/p-Si	Sol-gel	Au	UV/Visible	____	____	0.22 A/W at −5 V bias (420 nm)	____	[61]
n-ZnO/SiO2/p-Si	Ultrasonic Spray pyrolysis	Ni/Au; Ti/Pt/Au	UV/Visible	____	4.98×10−10 A (−1 V)	0.225–0.297 A/W at −1 V bias	____	[62]
Si particles coated n-ZnO/p-Si	RF Sputtering	Ni/Au; Ti/Au	UV/Visible	∼4 V	4.7×10−6 A/cm2 (−3 V)	____	____	[64]
n-ZnO/i-MgO/ p-Si	MBE	Ti/Au;In	UV	∼1.5 V	<1 nA (−2 V)	____	____	[65]
AlO coated n-ZnO/p-Si	RF Sputtering	Au-Al; In	UV/Visible	____	____	0.06 A/W at −5 V bias (310 nm)	____	[66]
n-ZnO/p-Si	RF Sputtering	Au-Al	UV/Visible	____	____	0.35 A/W at −5 V bias (650 nm)	____	[67]
Ni/n-ZnO/p-Si	DC magnetron sputtering	Ni	UV/Visible	____	1 μA (−8 V)	210 A/W (390 nm) and 110 A/W (850 nm) at −5 V bias	10−7 s	[68]
n-ZnO/p-GaN	MBE	Ni/Au; In	UV	4.6 V	____	∼10−6 A/W (370 nm) at 0 V bias	____	[69]