Highly Weak-light Sensitive and Dual-band Switchable Photodetector Based on CuI/Si Unilateral Heterojunction

doi:10.15541/jim20240094

Abstract

Abstract:

In recent years, copper iodide (CuI) is an emerging p-type wide bandgap semiconductor with high intrinsic Hall mobility, high optical absorption and large exciton binding energy. However, the spectral response and the photoelectric conversion efficiency are limited for CuI-based heterostructure devices, which is related to the difficulty in fabrication of high-quality CuI thin films on other semiconductors. In this study, a p-CuI/n-Si photodiode has been fabricated through a facile solid-phase iodination method. Although the CuI thin film is polycrystalline with obvious structural defects, the CuI/Si diode shows a high weak-light sensitivity and a high rectification ratio of 7.6×10⁴, indicating a good defect tolerance. This is because of the unilateral heterojunction behavior of the formation of the p⁺n diode. In this work, the mechanism of photocurrent of the p⁺n diode has been studied comprehensively. Different monochromatic lasers with wavelengths of 400, 505, 635 and 780 nm have been selected for testing the photoresponse. Under zero-bias voltage, the device is a unilateral heterojunction, and only visible light can be absorbed at the Si side. On the other hand, when a bias voltage of -3 V is applied, the photodiode is switched to a broader “UV-visible” band response mode. Therefore, the detection wavelength range can be switched between the “Visible” and “UV-visible” bands by adjusting the bias voltage. Moreover, the obtained CuI/Si diode was very sensitive to weak light illumination. A very high detectivity of 10¹³-10¹⁴ Jones can be achieved with a power density as low as 0.5 μW/cm², which is significantly higher than that of other Cu-based diodes. These findings underscore the high application potential of CuI when integrated with the traditional Si industry.

Key words: copper iodide, heterojunction, photodetector

CLC Number:

TQ174

YANG Jialin, WANG Liangjun, RUAN Siyuan, JIANG Xiulin, YANG Chang. Highly Weak-light Sensitive and Dual-band Switchable Photodetector Based on CuI/Si Unilateral Heterojunction[J]. Journal of Inorganic Materials, 2024, 39(9): 1063-1069.

Figures/Tables 7

Fig. 1 Fabrication and testing schematic diagram (a) Schematic structure of the fabricated p+n type CuI/Si heterojunction diode; (b) Schematic diagram of the photodiode test

Fig. 2 Structural and electrical characterization of the obtained CuI thin film (a) XRD pattern; (b) PL spectrum; (c) Optical transmittance; (d) SEM image

Fig. 3 I-V characteristic curve of the CuI/Si heterojunction

Fig. 4 I-V characteristic curves of the CuI/Si photodiode under different laser light wavelengths with a light power density of 50 μW/cm2 Dark current is plotted in dashed line; Colorful figure is available on website

Fig. 5 Responsivity of the CuI/Si photodiode as a function of light power density and responsivity under specific light intensity (a) 0 V bias applied; (b) -3 V bias applied; (c) 0 V bias applied under specific light intensity; (d) -3 V bias applied under specific light intensity

Table 1 Device parameters of the CuI/Si photodiodes

Wavelength/nm	Bias voltage/V	Responsivity (Weak/strong light)/(A·W^-1)	D* (Weak/strong light)/ (×10¹³, Jones)	EQE (Weak/strong light)/%
400	0	0.08/0.06	0.363/0.241	26/17
400	-3	3.58/0.15	15.4/0.669	1109/48
505	0	0.31/0.14	1.35/0.618	77/35
505	-3	3.46/0.30	14.9/1.31	849/74
635	0	0.65/0.13	2.82/0.561	127/25
635	-3	4.00/0.90	17.3/3.88	782/175
780	0	1.15/0.20	4.94/0.844	182/31
780	-3	4.70/0.67	20.3/2.92	747/107

Table 2 Summarization of photoelectric properties in Si-based photodiodes

Diode structure	Wavelength/ nm	Power density/ (μW·cm⁻²)	Bias voltage/V	D*/Jones	Responsivity/ (A·W^-1)	EQE/%	Ref.
SnSe/Si	405	10	-4	3.4×10¹¹	0.21	-	[36]
	405	300	-4	3.0×10¹¹	0.18	-
	650	10	0	1.1×10¹¹	0.20	-
	650	300	0	1.0×10¹¹	0.17	-
MoS₂/Si	514	3	-2	2.2×10¹¹	1.25	-	[37]
MoS₂/Si	514	80	-2	8.0×10¹¹	0.90	-	[37]
Graphene-Si	730	10	-2	2.1×10⁸	0.35	-	[38]
Si/ZnO	550	-	-2	-	0.37	-	[39]
ZnTe-TeO₂/Si	350	-	0	4.0×10¹²	0.03	-	[43]
ZnTe-TeO₂/Si	850	-	0	1.4×10¹³	0.08	-	[43]
CuI/Si	400	0.5	-3	1.54×10¹⁴	3.58	1109	This work
	400	50	-3	6.69×10¹²	0.15	48
	780	0.5	0	4.94×10¹³	1.15	182
	780	50	0	8.44×10¹²	0.20	31

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