S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Electrical and Computer Engineering (전기·정보공학부) Theses (Ph.D. / Sc.D._전기·정보공학부)
Infrared Detection Using the Silicon Devices
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- 공과대학 전기·컴퓨터공학부
- Issue Date
- 서울대학교 대학원
- Avalanche multiplication; Franz-Keldysh effect; Near Infrared; NMOS GIDL; Positive and negative temperature coefficient; Pulse measurement; Responsivity; Tunneling current; Zener diode
- 학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 박영준.
- Lights in nature can be classified into various bands depending on the wavelength. Among the many types of light, near infrared (NIR) light has a wavelength of 780?2500 nm. The NIR wavelength band is widely used in various types of sensor devices, as well as in communication. Therefore, there is substantial demand for efficient and cost-effective NIR detectors. However, although materials such as InGaAs, Ge, and PbS are applied in detectors to detect NIR wavelengths, these materials are not compatible with the widely used and cost-effective Si-based integration process.
Thus, this dissertation focuses on detection of NIR light using a Si based device. However, the crucial obstacle in using Si as an NIR detection material is that it has band gap energy of 1.12 eV, and therefore, it does not absorb wavelengths longer than 1150nm. One possible solution is utilizing the Franz?Keldysh effect (FKE) in the Si devices. The FKE dictates that a semiconductor can absorb a photon with lower energy than the band-gap energy by tunneling the valence electrons to the conduction band in the presence of a strong electric field. This phenomenon can be used to detect infrared (IR) photons if the junction is biased in the FKE bias region.
In this dissertation, to investigate the detection of NIR with a Si-based device, we attempt to use the Zener diode and the NMOSFET, which can generate tunneling currents in the presence of a strong electric field. When a strong reverse bias is applied to the Zener junction, a tunneling current is generated
the NMOSFET also has a tunneling current when the bias condition generates a gate-induced drain leakage (GIDL) current. In such a bias condition for both devices, NIR with wavelengths of 1310nm and 1550nm, which have lower energy than the band-gap energy of Si, are irradiated to the Zener diode and the NMOSFET. In the case of the Zener diode, an avalanche multiplication is investigated to cause more absorption by applying an additional, stronger electric field than the normal reverse bias condition, which causes a tunneling current to flow. However, because the negative temperature coefficient is due to the Joule heat generation of the junction in the bias regime of the avalanche multiplication, the methodology of a pulsed bias scheme is applied to mitigate the unintentional increase in the junction temperature and the associated degradation of the photo-responsivity under a DC bias. Accordingly, the NMOSFET in the condition in which GIDL flows can also absorb wavelengths of 1310nm and 1550nm by FKE. Additionally, the photo-generated current can be amplified by avalanche multiplication under a strong electric field with the pulsed bias scheme between the drain and the substrate.
Thus, this dissertation concludes that Si-based junctions can be used to detect IR signals using the FKE generation followed by multiplication through the newly proposed methodology of pulse measurement, which minimizes both the thermal effect and the degradation of photo-responsivity.