• Journal of Sensor Science and Technology
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• v.12 no.2
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• pp.66-71
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• 2003

Pt/AlGaN Schottky-type UV photodetectors were designed and fabricated. A low-temperature AlGaN interlayer buffer was grown between the AlGaN and GaN film in the diode structure epitaxy to obtain crack-free AlGaN active layers. A comparison was then made of the structural, electrical, and optical characteristics of two different diodes: one with an AlGaN($0.5\;{\mu}m$)/n+-GaN(2 nm) structure (type 1) and the other with an AlGaN($0.5\;{\mu}m$)/AlGaN interlayer($150\;{\AA}$)/n+-GaN($3\;{\mu}m$) structure(type 2). A crack-free AlGaN film was obtained by the insertion of a low-temperature AlGaN interlayer with an aluminum mole fraction of 26% into the $Al_xGa_{1-x}N$ layer. The fabricated Pt/$Al_{0.33}Ga_{0.67}N$ photodetector had a leakage current of 1 nA for the type 1 diode and $0.1\;{\mu}A$ for the type 2 diode at a reverse bias of -5 V. For the photoresponse measurement, the type 2 diode exhibited a cut-off wavelength of 300 nm, prominent responsivity of 0.15 A/W at 280 nm, and UV-visible extinction ratio of $1.5{\times}10^4$. Accordingly, the Pt/$Al_{0.33}Ga_{0.67}N$ Schottky-type ultraviolet photodetector with an AlGaN interlayer exhibited superior electrical and optical characteristics and improved UV detecting properties.

• Korean Journal of Optics and Photonics
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• v.9 no.6
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• pp.428-432
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• 1998

We fabricated 1$\times$8 array of GaAs/AlGaAs quantum well infrared photodetectors for the long wavelength infrared detection which is based on the bound-continuum intersubband transition, and characterized its electrical and optical properties. The device was grown on SI-GaAs(100) by the molecular beam epitaxy and consisted of 25 period of 40 ${\AA} $ GaAs well and 500 ${\AA} $ $Al_{0.28} Ga_{0.72}$ As barrier. To reduce the possibility of interface states only the center 20 ${\AA} $ of the well was doped with Si ($N_D=2{\times}10^{18} cm^{-3}$). We etched the sample to make square mesas of 200$\times$200 $\mu\textrm{m}^2$ and made an ohmic contact on each pixel with Au/Ge. Current-voltage characteristics and photoresponse spectrum of each detector reveal that the array was highly uniform and stable. The spectral responsivity and the detectivity $D^＊$ were measured to be 180,260 V/W and $4.9{\times}10^9cm\sqrt{Hz}/W$ respectively at the peak wavelength of $\lambda$ =7.8 $\mu\textrm{m}$ and at T=10 K.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.659-662
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• 2018

We report the properties of infrared photodetectors based on two kinds of quantum dots(QDs): i) 2.0 ML InAs QDs by the Stranski-Krastanov growth mode(SK QDs) and ii) sub-monolayer QDs by $4{\times}[0.3ML/1nm\;In_{0.15}Ga_{0.85}As]$ deposition(SML QDs). The QD infrared photodetector(QDIP) structure of $n^+-n^-(QDs)-n^+$ is epitaxially grown on GaAs (100) wafers using molecular-beam epitaxy. Both the bottom and top contact GaAs layers are Si doped at $2{\times}10^{18}/cm^3$. The QD layers are grown with Si doping of $2{\times}10^{17}/cm^3$ and capped by an $In_{0.15}Ga_{0.85}As$ layer at $495^{\circ}C$. The photoluminescence peak(1.24 eV) of the SML QDIP is blue-shifted with respect to that (1.04 eV) of SK QDIPs, suggesting that the electron ground state of SML QDIP is higher than that of the SK QDIP. As a result, the photoresponse regime(${\sim}9-14{\mu}m$) of the SML QDIP is longer than that (${\sim}6-12{\mu}m$) of the SK QDIP. The dark current of the SML QDIP is two orders of magnitude smaller value than that of the SK QDIP because of the inserted $Al_{0.08}Ga_{0.92}As$ layer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.179-186
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• 2019

In this study, we investigated the structural properties of $Ga_2O_3$ thin films and the photo-electrical properties of metal-semiconductor-metal (MSM) photodetectors deposited by Ti/Au electrodes. $Ga_2O_3$ thin films were grown at different temperatures using metal organic chemical vapor deposition (MOCVD). The crystal phase of $Ga_2O_3$ changed from ${\varepsilon}$-phase to ${\beta}$-phase depending on the growth temperature. The crystal structure of ${\varepsilon}-Ga_2O_3$ was confirmed by X-ray diffraction (XRD) analysis and the formation mechanism of crystal structure was discussed by scanning electron microscopy (SEM) images. From the results of current-voltage (I-V) and time-dependent photoresponse characteristics under the illumination of external lights, we confirmed that the MSM photodetector fabricated by ${\varepsilon}-Ga_2O_3$ showed much better photocurrent characteristics in the 266 nm UV range than in the visible range.