The study of InAs/InGaAs dot-in-a-well structures for quantum dot infrared photodetectors

The study of InAs/InGaAs dot-in-a-well structures for quantum dot infrared photodetectors
김정섭양창재이재열하승규최원준Yasushi Nanishi윤의준
quantum dot; infrared; QDIP; DWELL; photodetector
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Theoretically, the quantum dot infrared photodetectors (QDIPs) have much higher sensitivity for normal incidence light than the quantum well infrared photodetectors (QWIP) due to the carrier confinement in the three-dimensional structure. Furthermore, the longer carrier lifetime of QDs leads to higher responsivity, higher operation temperature and lower dark current [1].To realize these benefits in practical uses, the density and size of QDs should be manipulated on purpose and the non-defective growth of QDs are required. Previously, we reported the suppression of abnormally large island formation and the enhancement of emission efficiency by using periodic arsine interruption [2]. To tune the density and size of QDs, the InGaAs layer has been used as a buffer layer and capping layer of QDs, so called InAs/InGaAs dot-in-a-well (DWELL) structure [3]. However, the effect of InGaAs layers on the QD growth and optical properties has not been fully understood yet. InAs QDs were grown on the different InGaAs buffer layers by using post growth interruption (GI) and observed by atomic force microscopy (AFM). The post GI means that the growth step in which the supply of all sources is paused after the QD deposition. The density of QDs decreased and their heights increased with increasing the time of the post GI in all cases of InGaAs buffer layers. The reduction rate of the density was faster in the case of low In content of the buffer layer. This implies the mechanism of material diffusion on the QD surface is subject to the condition of InGaAs buffer layer. As a result of low temperature photoluminescence (PL) at 14 K, the Ga diffusion from InGaAs buffer layer is dominant in case of high In content. For QDIP application, we grew n-type GaAs/intrinsic DWELL/n-type GaAs structures. After the fabrication of devices with a simple mesa structure, dark current depending on the bias and temperature was measured. We found that t
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