Semiconductor ultraviolet detectors

Razeghi, Manijeh; Rogalski, Antoni

doi:10.1063/1.362677

Cited by 1,352 publications

(676 citation statements)

References 123 publications

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“…The high spectral selectivity combined with high photosensitivity suggest the possibility of using ZnO NWs as "visible-blind" UV photodetectors for commercial, military, and space applications. 43 Figure 5a also shows that the photoresponsivity of the ZnO NW detector increases by about 2 orders of magnitude after keeping the sample under vacuum (P < 10 -4 Torr) for approximately 20 min. This increase in photocurrent is consistent with the increase of the electron lifetime due to a reduction in the oxygen readsorption rate in oxygen-deficient environments (Figure 2c), which is also supported by the spectral similarity of the photocurrent measured in air or in vacuum, indicating that the same physical processes are responsible for photoconduction.…”

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confidence: 87%

ZnO Nanowire UV Photodetectors with High Internal Gain

et al. 2007

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ZnO nanowire (NW) visible-blind UV photodetectors with internal photoconductive gain as high as G ∼ 10 8 have been fabricated and characterized. The photoconduction mechanism in these devices has been elucidated by means of time-resolved measurements spanning a wide temporal domain, from 10 -9 to 10 2 s, revealing the coexistence of fast (τ ∼ 20 ns) and slow (τ ∼ 10 s) components of the carrier relaxation dynamics. The extremely high photoconductive gain is attributed to the presence of oxygen-related hole-trap states at the NW surface, which prevents charge-carrier recombination and prolongs the photocarrier lifetime, as evidenced by the sensitivity of the photocurrrent to ambient conditions. Surprisingly, this mechanism appears to be effective even at the shortest time scale investigated of t < 1 ns. Despite the slow relaxation time, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products (GB) higher than ∼10 GHz. The high gain and low power consumption of NW photodetectors promise a new generation of phototransistors for applications such as sensing, imaging, and intrachip optical interconnects.Because of its wide band gap (E g ) 3.4 eV), low cost, and ease of manufacturing, ZnO is emerging as a potential alternative to GaN in optoelectronic applications, 1 including light-emitting diodes, laser diodes, and photodetectors for the UV spectral range. In the past decade, the demonstration of a large variety of functional ZnO nanowire (NW) devices such as field effect transistors, 2,3 optically pumped lasers, 4,5 and chemical and biological sensors 6 have aroused growing interest in this material. 7 In particular, ZnO NW photodetectors and optical switches have been the subject of extensive investigations. [8][9][10][11][12][13][14][15][16][17][18] Despite the abundant research on NW photoconduction, 19 the two main factors contributing to the high photosensitivity of such nanostructures have been scarcely recognized: (1) the large surface-to-volume ratio and the presence of deep level surface trap states in NWs greatly prolongs the photocarrier lifetime; (2) the reduced dimensionality of the active area in NW devices shortens the carrier transit time. Indeed, the combination of long lifetime and short transit time of charge carriers can result in substantial photoconductive gain. [20][21][22] In this letter, we present ZnO NW photodetectors with large photoresponse; upon UV illumination at relatively low light intensities (I ∼ 10 µW/cm 2 ), the current in ZnO NWs increases by several orders of magnitude, which translates to a photoconductive gain of G > 10 8 . To elucidate the photoconduction mechanism that involves fast carrier thermalization and trapping at the NW surface and electronhole recombination at extended and localized states, we have studied the photoconductivity of ZnO NWs by time-resolved measurements and in different ambient conditions (e.g., in air or under vacuum). A physical model was developed to illustrate the origin of the photoconductive gain in ...

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confidence: 87%

ZnO Nanowire UV Photodetectors with High Internal Gain

et al. 2007

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“…At higher applied bias voltages, the measured responsivity exhibited photoconductive gain, probably originating from defects at the surface and/or within the depletion layer. Then, it tends to saturate due to sweep-out effect [28]. Comparing the ratio of the zero bias and the saturated peak responsivity for all three devices, almost a constant value is found, indicating the effect of the barrier thickness.…”

Section: Models and Discussionmentioning

confidence: 91%

GaN/AlGaN back-illuminated multiple-quantum-well Schottky barrier ultraviolet photodetectors

Teke

Doğan

Yun

et al. 2003

Solid-State Electronics

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We report on characterization and operation principle of a set of GaN/AlGaN multiple-quantum-well (MQW) photovoltaic detectors. The structures were grown by molecular beam epitaxy (MBE) on c-plane sapphire substrates and fabricated in the back-illuminated vertical Schottky geometry. Introduction of MQWs into the active region of devices is expected to enhance the quantum efficiency due to the high absorption coefficient. A nearly flat spectral responsivity between 325 and 350 nm with 0.054 A/W peak responsivity was achieved from the single-side polished backside (rough) illuminated GaN/AlGaN MQW devices. The cutoff wavelength of the MQW photodetector can be tuned by adjusting the well width, well composition and barrier height. A model has been developed to gain insight into the operation principles of MQWs photodiodes. The peak responsivity increased with decreasing barrier thickness due to enhanced tunneling of photogenerated carriers.

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“…1,2 On the other hand, various recombination processes directly affect the sensitivity of light detection for a wide spectral range. 3,4 Therefore, it is essential to characterize various recombination rates of the active photonic materials for determining the required conditions to achieve the best performance. In previous work, the Auger recombination for a Type-II multiple quantum well (MQW) structure was characterized, and the non-threshold Auger recombination in those systems was demonstrated.…”

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Observation of suppressed Auger mechanism in type-I quantum well structures with delocalized electron-hole wavefunctions

2015

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We report the first observation of non-threshold Auger mechanism for a quantum well structure with Type-I band alignment. Excitation-dependent photoluminescence measurements were used to extract the Auger recombination coefficients from 77 K up to room temperature. The results verify the role of interface mediated momentum exchange as well as suppression of Auger recombination for delocalized electron-hole wavefunctions.

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Semiconductor ultraviolet detectors

Cited by 1,352 publications

References 123 publications

ZnO Nanowire UV Photodetectors with High Internal Gain

ZnO Nanowire UV Photodetectors with High Internal Gain

GaN/AlGaN back-illuminated multiple-quantum-well Schottky barrier ultraviolet photodetectors

Observation of suppressed Auger mechanism in type-I quantum well structures with delocalized electron-hole wavefunctions

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