Simulation of mushroom-typed modified near-ballistic uni-traveling-carrier photodetector with sub-THz operational bandwidth

Infrared Focal Plane Array (IRFPA) of InSb is designed to work under the condition of zero bias voltage or nearly to zero bias voltage. InSb IRFPA can't work normally if PN junction is in the condition of high reverse bias voltage for several minutes. In order to analyze the causation of the phenomena some experiments were designed to simulate the condition of high reverse bias voltage. It is found that when the reverse bias voltage exceeds the limited value, the responsibility of InSb detector becomes lower. The phenomena will not change unless the operating temperature is raised to room temperature and kept for a long time. Response characteristic of InSb PN junction under high reverse bias voltage is briefly described in this paper. The factors affecting response characteristic are discussed. The limited value of the reverse voltage is given. The result is useful to design the driving circuit of InSb IPFPA. It also plays the guidance part in application of InSb detector.

The confined states in [001]-oriented strained silicon layers embedded in oxide are investigated using dasiafull-zonepsila k.p analysis within the envelop function approximation and Tight-Binding (TB) model. Calculations of important transport parameters - energy band shifts and transport masses - show new results, rising the issues of the limit of simple models like the Effective Mass Approximation (EMA).

The holes confined states in [001] -oriented 5 nm-thick relaxed silicon layer embedded in oxide are investigated using full-band k.p method within the envelop function approximation. Full-band calculations of important transport parameters - energy band shifts, curvature masses and density-of-state masses - show new results, rising the issues of the limit of simple models like the Effective Mass Approximation (EMA) and the 6-level k.p model.

On the validity of the effective mass approximation and the Luttinger k.p model in fully depleted SOI MOSFETs

Most of optical signals is collected using optical instruments. Although photodiodes have the same unilateral conductivity as ordinary diodes, it can act as a photoelectric sensor in circuit and play a significant role in signal acquisition. In this study, the photosensitivity of photodiode was studied, a circuit was designed selecting photodiode as photoelectric sensor, and the signal acquisition was realized by testing the feasibility of the designed circuit. The equivalent model of the designed circuit was established by Pspice software, and the circuit performance under different illumination and bias voltage was simulated and analyzed. It is concluded that the photodiode circuit designed in this paper could effectively reflect the intensity of optical signals. When the optical signal was fixed, the increase of the reverse bias voltage in a certain range increased the photocurrent in the circuit; as a result, the signal was enhanced. The reverse bias voltage should not exceed 90 V; otherwise the dark current in the circuit would interfere with the detection of optical signals. The designed circuit can collect the pulse optical signal effectively and adjust the response characteristics of the circuit through the reverse bias voltage; the higher the bias voltage in a certain range, the better the response characteristics.

The influence of tension deformation on the electrical parameters of semiconductor films of crystalline silicon is considered. The influence of the ratio of thicknesses of the film and deforming germanium substrate on the shift of energy bands and variation in the mobility of free charge carriers is taken into account. The dependence of resistance of the strained anisotropic n-channel of the field-effect transistor on the size of current contacts and the value of the deformation is obtained and analyzed. It is shown that resistance of the strained silicon channel of the field-effect transistor in the open state is determined not only by its sizes and electrical parameters but also by the thickness of the deforming substrate and by the sizes of current contacts.

Chapter 2 - The energy gap of clusters, nanoparticles, and quantum dots

Band alignments tuned by spontaneous polarization in two-dimensional MoS2/GaN van der Waals heterostructures

Interface charging and intercalations effects on d-band transition metal diselenide photoelectrodes

The properties of charge carrier traps in the oxide bulk, at high-k/silicon transition regions, at the silicon interface and as dipoles are discussed from physical and electrical perspectives. In order to elucidate the charging properties of oxide traps the statistical mechanics for occupation is derived based on a constant pressure ensemble and used to interpret the influence of negative-U states. For the transition region close to the silicon interface, the existence of unstable traps in the shift of energy band between SiO2 and HfO2 with continuous modification is pointed out. The physical background for electrical measurements on interface states is examined and, finally, dipoles constituted by traps in high-k dielectrics for regulating threshold voltage of MOS transistors are considered.

Microplasmas have attracted more and more attention due to their unique characteristics, and breakdown voltage is an important parameter for microplasma devices, particularly for addressable arrays of microplasma devices. However, small changes in shape or interface would bring obvious change in breakdown voltage. In this paper, five groups of simulations of breakdown voltage were operated under different geometry parameters to develop the trend of breakdown voltage following geometrical size under different operation pressures. The drift-diffusion approximation model is adopted in these simulations. The simulation results show that breakdown voltage will increase with the increase in the microcavity depth and thickness of the dielectric. Therefore, the breakdown voltage will reduce when microcavity width increases. The less is the microcavity size, the less is breakdown voltage, and the higher is the pressure corresponding to minimum breakdown voltage, which shows that the decrease in microcavity size can develop operation pressure and decrease breakdown voltage obviously.

Physical processes in organic solar cells

In this paper, an InP-based mesa-structure uni-traveling-carrier photodetector is designed. By adopting Gaussian doping scheme in the absorption layer and incorporating an appropriate cliff layer, high speed and high saturation current characteristics are both achieved simultaneously. For the device with a 14 μm2 active area, the simulated results indicate that the bandwidth reaches 58 GHz and DC saturation current increases up to 158 mA at a reverse bias of 2 V. Under high optical injection, the bandwidth degradation and current saturation are studied, which are caused by energy band shift and electric field collapse.

为了优化PIN光电探测器响应特性，首先依据载流子速率方程，并考虑芯片寄生参量和封装寄生参量，建立光电探测器的等效电路模型。然后仿真分析了反偏电压、I区宽度、光敏面、芯片寄生电阻和电容、封装寄生电阻、电容和电感对光电探测器脉冲响应特性和频率响应特性的影响。结果表明：通过增大反偏电压，减小光敏面和寄生参量(芯片寄生电容和电阻，封装寄生电容和电阻)，选取合适的I区宽度，利用引线电感的谐振效应现象，可以抑制脉冲响应波形畸变，提高频率响应带宽。

Gate breakdown characteristics of MgO/GaN MOSFETs