Enhancement of Metal-Oxide-Semiconductor Tunneling photodetectors and Light Emitting Diode

本論文中，我們提出利用金氧半穿隧二極體中大閘極電流的特性來製作光偵測器。由於載子會穿隧過薄氧化層形成漏電流，使得元件操作在深空乏狀態。因此元件的暗電流受限於空乏區中所產生的少數載子。利用高溫成長氧化層可使元件暗電流下降。 對光偵測器來說，除了響應之外，頻寬亦為一重要的指標。為了增加金氧半光偵測器之頻寬，我們提出利用操作於完全空乏下之新型矽在絕緣層上(SOI)金氧半光偵測器結構。對一具有高摻雜濃度緩衝層之元件來說，其頻寬高達 22 GHz，並且完全可整合於ULSI技術。若元件的吸收層夠薄，則頻寬將完全由飄移電流決定。若吸收層太厚，則必須同時考慮擴散電流。分佈式布拉格反射鏡也用來設計元件結構以增加響應。 我們也成功的利用氧化鉿當作金屬-介電層-半導體(MIS)發光二極體結構中的介電材料來。根據電通量不變的定律，在矽與介電質的介面下，矽會因為比較大的電通量而產生比較多的電洞聚集在介面，因此增加發光效率。氧化鉿的發光效率為氧化矽的四倍。 表面電漿子可以應用在金氧半發光二極體上以增加發光效率。藉由控制鋁薄膜上的洞陣列的大小與間隔，我們可以讓矽發光有更高的穿透率。 這些簡單卻具有發展潛力的矽基金氧半光偵測器可配合其他的光電元件使用，並可作為未來光訊號處理及矽晶片中光電應用功能的基石。In this thesis, the novel metal-oxide-semiconductor (MOS) tunneling diodes with high leakage current were utilized as photodetectors. The leakage of inversion carrier through ultrathin oxide makes the device to operate in the deep depletion region. The dark current is limited by the thermal generation process and can be reduced by the high growth temperature of oxide. In order to increase the speed of the MOS tunneling photodetectors, the novel fully-depleted silicon-on-insulator (SOI) MOS photodetector is proposed. For devices with 1020 cm-3 buffer layer doping, the device can reach high bandwidth (22 GHz) and are fully compatible with ultra-large scale integration (ULSI) technology. For thin devices, the transit time can be determined by the drift mechanism. For thick devices, however, the diffusion mechanism is needed to describe the device behavior. DBR (distributed Bragg reflector) model is used to design the device for better responsivity. The metal-insulator-semiconductor light emission diode (MIS LED) using high k insulators is successfully demonstrated. The enhancement of quantum external efficiency of MIS LED is accomplished well due to more quantum confinement holes created by larger electric field on Si. From the simulations, it is confirmed that the electric field on Si is increased when HfO2 replaced SiO2. The long wavelength EL spectrum is observed for the high k LED with many interface states. The normalized EL spectrum of MOS LED and high k LED are similar. The quantum efficiency of high k LED is 2 * 10-6, which is about ten times larger than oxide LED. Surface plasmon is applied on MOS LED for better light intensity. By controlling the size of hole array, we can have enhanced transmission for silicon emitted light through Aluminum film. These simple and high performance Si-based photodetectors together with other devices can be used as building blocks for the future optical signal process and the optoelectronic applications on Si chips.Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Thesis Organization 2 Chapter 2 Si NMOS Photodetector 4 2.1 Device Operation 4 2.2 Derivation of quantum efficiency in NMOS device 7 2.3 Summary 14 Chapter 3 Si-based Fully-depleted silicon-on-Insulator (SOI) MOS Photodetectors with Ultrahigh Bandwidth 15 3.1 Introduction 15 3.2 Device Simulation Details 16 3.3 Simulation Results and Discussion 18 3.4 Analytical Model 24 3.4.1 Drift Current Model 25 3.4.2 Diffusion Current Model 29 3.5 Bragg reflector consideration 33 3.6 Experimental result of bandwidth 40 3.7 summary 41 Chapter 4 Metal-Insulator-Silicon (MIS) Light-Emitting Tunneling Diodes 42 4.1 Introduction 42 4.2 Operation Principle 42 4.3 Electroluminescence of MOS Tunneling Diodes 45 4.4 Light Emission from Al/HfO2/Silicon Diodes 47 4.5 ummary 54 Chapter 5 Plasmon enhance transmission and direction 55 5.1 Bulk plasmon theory 55 5.2 Surface plasmon theory 56 5.2.1 Dispersion relation 57 5.2.2 Excitation of surface plasmon by light with grating coupler 60 5.2.3 Transmission through hole array 61 5.3 Prediction of Surface plasmon for silicon MOS LED 64 5.3.1 Effective dielectric function of metal film 64 5.3.2 Thickness dispersion on dielectric film 65 5.4 Summary 66 Chapter 6 Summary and future work 67 6.1 Summary 67 6.2 Future work 68 Reference 7