| 초록 |
Quantum dot infrared photodetectors (QDIPs) have several advantages over quantum-well IR photodetectors (QWIPs). Three-dimensionally confined QDs make QDIPs intrinsically sensitive to normally incident radiation, unlike QWIPs. Given the phonon bottleneck effects, QDs can also have longer carrier relaxation time than QWs. Thus, QDIPs have potentially lower dark current and relatively higher photoelectric gain. The performance of QDIPs is affected by various factors such as QDIP structure, carrier doping, and growth conditions. Among them, QD size and shape are the most important factors determining the nature characteristics of QD inter and intraband transitions for IR detection. Two types of InAs/GaAs quantum dots (QDs), namely, relatively large/steep QDs and small/shallow QDs, are comprehensively studied for QD infrared photodetector (QDIP) applications. The QDIP with small QDs shows a broad photoresponse over a relatively wide range (~5 μm to 7 μm), whereas its QDIP counterpart with large QDs yields a sharp photoresponse peak at ~7.2 μm with a full width at half maximum of 32 meV. The systematic interband and intraband studies suggest that the excited states involved in intraband transitions in QDIPs with small and large QDs have continuum and QD-bound states, respectively. The QDIP with large QDs shows higher photocurrent-to-dark current ratio than the QDIP with small QDs. |
