Visible-Blind UV Digital Camera Based On a 32 × 32 Array of GaN/AlGaN p-i-n Photodiodes

Brown, J.D.; Yu, Zhonghai; Matthews, John; Harney, S.; Boney, J.; Schetzina, J. F.; Benson, J. D.; Dang, Kim; Terrill, C. W.; Nohava, Thomas; Yang, Wei; Krishnankutty, S.

doi:10.1557/s109257830000065x

Cited by 58 publications

(27 citation statements)

References 14 publications

(12 reference statements)

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“…For low noise detection, detectivity should be as high as possible. The typical detectivity of a cooled PMT is about cm Hz W around 300 nm [13]. A comparable detectivity performance ( cm Hz W at 275 nm) was reported recently with a solar-blind AlGaN-based back-illuminated p-i-n photodiode [14].…”

supporting

confidence: 79%

Solar-Blind AlGaN-Based p-i-n Photodiodes With Low Dark Current and High Detectivity

Bıyıklı

Kimukin

Aytür

et al. 2004

IEEE Photon. Technol. Lett.

120

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Abstract-We report solar-blind Al Ga 1 N-based heterojunction p-i-n photodiodes with low dark current and high detectivity. After the p+ GaN cap layer was recess etched, measured dark current was below 3 fA for reverse bias values up to 6 V. The device responsivity increased with reverse bias and reached 0.11 A/W at 261 nm under 10-V reverse bias. The detectors exhibited a cutoff around 283 nm, and a visible rejection of four orders of magnitude at zero bias. Low dark current values led to a high differential resistance of 9.52 10 15 . The thermally limited detectivity of the devices was calculated as 4.9 10 14 cm Hz 1 2 W 1 .Index Terms-AlGaN, dark current, detectivity, heterostructure, high-performance, p-i-n photodiode. SOLAR-BLIND detectors with long-wavelength cutoff around 280 nm have important applications including missile plume sensing, flame detection, chemical-biological agent sensing, and covert space-to-space communications [1]. With the advent in material growth of high-quality Al Ga N ternary alloys, AlGaN-based solar-blind photodetectors emerged as a potential alternative for the photomultiplier tube (PMT) and silicon-based solar-blind detector technology. They have the advantage of intrinsic solar-blindness, and therefore, do not need complex and costly filters. In addition, AlGaN-based solar-blind detectors can operate under harsh conditions due to their wide bandgap and robust material properties [2]. Several research groups have demonstrated high-performance solar-blind photodetectors using Al Ga N material systemDetectivity is an important detector performance parameter which gives the signal-to-noise performance of the device. For low noise detection, detectivity should be as high as possible. The typical detectivity of a cooled PMT is about cm Hz W around 300 nm [13]. A comparable detectivity performance ( cm Hz W at 275 nm) was reported recently with a solar-blind AlGaN-based back-illuminated p-i-n photodiode [14]. In this letter, we report the design, fabrication, and characterization of solar-blind AlGaN p-i-n photodiodes with record dark current and detectivity performance. The measured dark current was below 3 fA at 6-V re- verse bias and a PMT-exceeding solar-blind detectivity of cm Hz W at 267 nm was achieved. The p-i-n photodiode wafer was grown by metal-organic chemical vapor deposition on sapphire substrate. The detector structure was designed for front (p-side) illumination. The active absorption region of the photodiode was formed with a 100-nm-thick unintentionally doped Al Ga N layer which was sandwiched between a 250-nm-thick n+ GaN layer and a 10-nm-thick p-type-doped Al Ga N layer. To improve the p-ohmic contact quality, a 30-nm-thick p-type GaN cap layer was grown on top of p-Al Ga N layer. A five-step microwave compatible semiconductor fabrication process was utilized to complete the device fabrication [15]. In the first two steps, ohmic contacts were formed. A 250-nm deep dry-etch for n+ ohmic contact was done via CCl F -based reactive ion etching (RIE). This was follow...

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supporting

confidence: 79%

Solar-Blind AlGaN-Based p-i-n Photodiodes With Low Dark Current and High Detectivity

Bıyıklı

Kimukin

Aytür

et al. 2004

IEEE Photon. Technol. Lett.

120

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“…It shows that the ratio reaches about 63 at around -3.5 V. This is expected since the dynamic resistance of a photodiode becomes maximum near the zero-bias condition. 33 Such a high value of the photo-to-dark current ratio indicates that the structure is most sensitive to UV photons at around -3.5 V. Photocurrents (I P ) were measured by irradiating the sample with light of wavelength k at a fixed bias voltage. Figure 4 shows the results of the spectral response of the photocurrent measurements at the three bias voltages of -1, -2, and -5 V. It is observed that, irrespective of the bias voltage, there is only a small rise in the photocurrent value from 750 nm onwards, resulting in a broad hump extending to 450 nm.…”

Section: Resultsmentioning

confidence: 99%

Ultraviolet Photodetection Properties of a Pt Contact on a Mg0.1Zn0.9O/ZnO Composite Film

Mridha

Ghosh

Basak

2007

Journal of Elec Materi

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We report on the ultraviolet (UV) photodetection properties of a Pt contact on a sol-gel Mg 0.1 Zn 0.9 O/ZnO composite structure on a glass substrate. In the dark, the current-voltage (I-V) characteristics between the Pt and Ag contacts on the top of the ZnO film were linear while that on the Mg 0.1 Zn 0.9 O/ZnO composite film were rectifying, suggesting the formation of a Schottky diode on the latter. The ideality factor, n, and the reverse leakage current density, J R , of the Schottky diode were greater than 2 and 2.36 · 10 -2 A cm -2 at -5 V, respectively. Under ultraviolet light, the I-V characteristics become linear. The maximum photo-to-dark current ratio observed was about 63. The composite film showed good sensitivity to UV light with wavelengths of less than 400 nm, though the photoresponse process was found to be slow.

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“…To that end, we use a model originally introduced by Bube for the case of Hall effect in inhomogeneous materials. 19 Since the GaN film is known to grow in columnar structure, it may be viewed as composed of two materials: one represents the bulk of each grain and possesses low resistivity, 1 ; the other has high resistivity, 2 , representing the grain boundaries, where defects trap charges and repel free carriers. The added resistivity of the grain boundaries gives rise to an additional Hall voltage produced over these boundaries.…”

Section: Modelmentioning

confidence: 99%

“…2 For lack of adequate GaN substrates, GaN films are commonly grown on substrates to which they are both lattice and thermally mismatched. Typical growth process starts with the formation of a highly defective nucleation layer at temperatures lower than the typical growth temperature providing a bridge over the lattice mismatch.…”

Section: Introductionmentioning

confidence: 99%

Hall photovoltage deep-level spectroscopy of GaN films

et al. 2001

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Spectroscopy of photoinduced changes in semiconductor Hall voltage is proposed as a method to characterize deep levels. An analytical expression for the Hall coefficient as a function of the charge trapped at grain boundaries is derived. The experimental Hall voltage is demonstrated by measuring thin films of GaN grown on sapphire and is shown to be consistent with the model. The Hall voltage spectrum is correlated to spectra from three other deep-level spectroscopies: photoluminescence, photoconductivity, and surface photovoltage, obtained under the same conditions from the same sample. Comparing spectra from the various spectroscopies shows that the yellow-luminescence-related deep states in GaN are charged in equilibrium and discharged by the exciting photons, and suggests that the blue-luminescence-related states are deep donors positioned 2.8 eV above the valence band and neutral in equilibrium.

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Visible-Blind UV Digital Camera Based On a 32 × 32 Array of GaN/AlGaN p-i-n Photodiodes

Cited by 58 publications

References 14 publications

Solar-Blind AlGaN-Based p-i-n Photodiodes With Low Dark Current and High Detectivity

Solar-Blind AlGaN-Based p-i-n Photodiodes With Low Dark Current and High Detectivity

Ultraviolet Photodetection Properties of a Pt Contact on a Mg0.1Zn0.9O/ZnO Composite Film

Hall photovoltage deep-level spectroscopy of GaN films

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