Novel Metal-Insulator-Semiconductor Photodetectors
Date Issued
2004
Date
2004
Author(s)
Kuo, Ping-Sheng
DOI
en-US
Abstract
In this thesis, the metal-oxide-semiconductor (MOS) tunneling diodes were utilized as photodetectors based on that the gate current has a photo-response. We use liquid phase deposition (LPD) method instead of traditional thermal method to deposit oxide films, and the LPD has a higher efficiency due to more defects in it. By adding NH4OH into LPD solution, we find the N atoms can reduce defects in oxynitride and the film with fewer defects has a lower current and higher operation temperature in long wavelength range (2~10 μm). Recessed oxynitride dots are demonstrated by depositing LPD oxynitride on Ge quantum dots substrate and they have a higher dot height than oxide dots.
To increase the cutoff wavelength and efficiency of the MOS detector, Ge and Ge/Si quantum dots are used as absorption layers. The oxide is directly grown on Ge substrate by liquid phase deposition to reduce thermal budget. This Ge photodetector can operate at 1.3 and 1.5 μm lightwave and can be applied to the fiber-optic communications. The maximum external quantum efficiency is estimated approximately 50 %, and responsivity can reach 0.5 A/W at 1.5 μm. The five-period Ge quantum dot MOS device can detect the wavelengths of 820 nm, 1300 nm, and 1550 nm with the responsivity of 130, 0.16, and 0.08 mA/W, respectively. The responsivity at 850 nm reaches 600 mA/W using a 20-period Ge quantum dot absorption layer.
Finally, the MOS Ge/Si quantum dot infrared photodetectors (QDIPs) for 2 ~ 10 μm using hole inter-valance subband transitions are demonstrated. The maximum operating temperature is 140 K for 3 ~ 10 μm and is up to 200 K for 2 ~ 3 μm detection with LPD oxynitride.
We also attempt to use different metal instead of aluminum to form the electrode. Because of the platinum has a higher workfunction, the current transition mechanism is different. For Ge quantum dots devices with platinum gate, the current has photo-response under both positive and negative bias. So the dual-polarity operable MOS photodetector is demonstrated. In addition, we also study the hole blocking effect which can effectively lower the hole current. With the lower temperature, the holes confined in the dots can obtain less energy to jump out of the dots.
Subjects
光偵測器
量子點
鍺
鉑
photodetector
Ge
Pt
quantum dot
Type
thesis
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