以分子束磊晶製備之量子點紅外線光偵測器

Quantum-Dot Infrared Photodetectors Prepared by Molecular Beam Epitaxy

陳政男(Cheng-Nan Chen)

指導教授 ： 吳孟奇

國立清華大學/電機資訊學院/電子工程研究所/碩士(2008年)

https://doi.org/10.6843/NTHU.2008.00694

摘要

In this thesis, ten-period quantum-dot infrared photodetectors (QDIPs), single-period QDIPs and quantum-dot (QD)/quantum-well (QW) mixed-mode infrared photodetectors (MMIPs) prepared by molecular beam epitaxy (MBE) are investigated. With uniform QD size distribution, wide detection window and high responsivities are observed for the 10-period QDIP. The wide spectral response is attributed to the summation of transitions between the QD excited states and the wetting layer (WL) state instead of transitions between QD ground state and higher excited states. With the Fermi level raised from near or below the ground state to close or above the excited state, the single-period QDIPs with no response, highest response and depressed response are observed. The phenomenon is attributed to three different electron occupancy situations at the QD region resulted from the position of the flat-band Fermi level. The results suggest that unlike quantum-well infrared photodetectors (QWIPs), wide Fermi level tuning range is available for QDIPs, which is advantageous for dark current depression to achieve high-temperature operation. Also observed is the decrease of barrier heights with increasing Fermi level position in the QD structure. The phenomenon is attributed to the acceptor-like behavior of the depleted QD such that the p-type GaAs barrier height would be pushed higher. Larger QD sizes in both height and diameter and more uniform size distribution are observed for the migration-enhanced (MEE)-grown sample. The 10-period QDIP with QDs grown by MEE mode has revealed longer detection wavelength and reduced normal-incident absorption. The phenomenon reveals that beside the reduction of energy difference between confinement states, larger QD sizes would also depress the normal-incident absorption predicted for the theoretical zero-volume QD structures. To achieve multi-color detection within a single device structure, MMIPs are demonstrated to perform multi-color detection at both mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) ranges. The polarization-dependent spectral responses have shown that the higher normal-incident absorption is observed for the MWIR peaks, which suggest that the intraband transitions in the QD structure are responsible for the MWIR peaks while the intraband transition in the QW region for the LWIR peak. A model is also established to explain the transition mechanisms of the MMIPs.

關鍵字

紅外線光偵測器 ； 遷移增強式 ； 正面入射吸收 ； 多重顏色之偵測 ； 躍遷機制

並列摘要

無資料

並列關鍵字

infrared photodetectors ； migration-enhanced ； normal-incident absorption ； multi-color detection ； transition mechanisms

參考文獻

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