Optical and Electrical Characterization of Quantum Dot Infrared Photodetector Structure Treated with Hydrogen-Plasma
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Optical and Electrical Characterization of Quantum Dot Infrared Photodetector Structure Treated with Hydrogen-Plasma H.D.Nam1,2,J.D.Song1,W.J.Choi1*,J.I.Lee1, H.S.Yang2 1 Nano-Device Reasearch Center, Korea Institute of Science and Technology, P.O.Box 131 Cheongryang, Seoul 130-650, Korea. 2 Dept. of Physics, Chung-Ang University, Seoul 156-756, Korea. * contact author: [email protected] ABSTRACT We have carried out hydrogen-plasma (H-plasma) treatments on a quantum dot infrared photodetector (QDIP) structure, with a 5-stacked InAs dots in an InGaAs well structure and a Al0.3Ga0.7As/GaAs superlattice barrier. The sample structures were grown by molecular beam epitaxy. The H-plasma treatment has been carried out at 150 oC for 3 min – 40 min with 40 sccm of H2 gas flow rate and 10 W of RF power. After H-plasma treatment, photoluminescence (PL) intensities of the samples were slightly reduced compared to that of as-grown sample, without any changes in their PL peak position. The dark currents of H-plasma treated samples were much smaller by many orders of magnitudes than that for as-grown sample. The sample exposed to Hplasma for 10 min showed the lowest dark current, enabling the observation of photocurrent with a wide spectrum between 3 – 12 µm at 11 K. INTRODUCTION Recently various zero-dimensional quantum structures utilizing self-assembled QDs have been fabricated due to progresses in growth technology [1]. The QD structures with the highly strained structure and low growing temperature have defects, which might strongly degrade device performances. Several post-growth processes have been investigated as means to improve the performances of devices such as QD lasers and detectors [2 - 5]. One of those processes is a thermal annealing, which has been reported to reduce non-radiative recombination centers like defects and consequently enhance the photoluminescence (PL) intensity [2 - 5]. However, this process has been known to induce the degradation of electrical properties, such as large dark currents, which obscured the photocurrent signal and prevented further measurements especially in quantum dot infrared detectors (QDIPs) [6]. Another method for post-growth processes is hydrogen passivation. Hydrogen has been reported to play an important role in passivating interfacial defects like dislocations in heteroepitaxial layers [7]. In optoelectronic devices,
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defects lead to non-radiative centers and hence higher threshold and shorter device lifetime in lasters. Defects also lead to large dark currents in QDIPs. Hydrogen-incorporation in semiconductors can lead to a reduction of these non-radiative centers and dislocations. Recently, several studies of hydrogen-plasma treatment on QD structures have been focused mainly on optical properties such as PL spectrum [8 - 10]. In this study, we investigated the hydrogen effect on a QDIP. The materials characteristics such as PL spectra and device performances such as dark current and photo response have been studied and compared for as-grown and H-plasma
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