The electron, gamma and neutron radiation degradation of III-V semiconductors and heterojunction bipolar transistors (HBTs) is investigated in this thesis. Particular attention is paid to InP and InGaAs materials and InP/InGaAs abrupt single HBTs (SHBTs). Complete process sequences for fabrication of InP/InGaAs HBTs are developed and subsequently employed to produce the devices, which are then electrically characterized and irradiated with the different types of radiation. A comprehensive analytical HBT model is developed and radiation damage calculations are performed to model the observed radiation-induced degradation of SHBTs. The most pronounced radiation effects found in SHBTs include reduction of the common-emitter DC current gain, shift of the collector-emitter (CE) offset voltage and increase of the emitter, base and collector parasitic resistances. Quantitative analysis performed using the developed model demonstrates that increase of the neutral bulk and base-emitter (BE) space charge region (SCR) components of the base current are responsible for the observed current gain degradation. The rise of the neutral bulk recombination is attributed to decrease in a Shockley-Read-Hall (SRH) carrier lifetime, while the SCR current increase is caused by rising SCR SRH recombination and activation of a tunneling-recombination mechanism. On the material level these effects are explained by displacement defects produced in a semiconductor by the incident radiation. The second primary change of the SHBT characteristics, CE offset voltage shift, is induced by degradation of the base-collector (BC) junction. The observed rise of the BC current is brought on by diffusion and recombination currents which increase as more defects are introduced in a semiconductor. Finally, the resistance degradation is attributed to deterioration of low-doped layers of a transistor, and to degradation of the device metal contacts. / Graduation date: 2001

When electronic components are to be used in systems destined for operation in the extraterrestrial environment, one must be concerned about the effects of the naturally occurring radiation in outer space. For example, power metal-oxide-semiconductor-field-effect transistors (MOSFETs) and power bipolar junction transistors (BJTs) are susceptible to a phenomenon called single-event burnout (SEB) which may result from bombardment by heavy ions originating from the nuclear reactions within the sun and other stars. SEB is a catastrophic failure mechanism initiated by the passage of a heavy ion through sensitive regions of the power MOSFET or power BJT. The main thrust of this dissertation is an analytical model describing the device-related aspects of the SEB mechanism. Physical device parameters such as doping concentrations, dimensions of various regions, and operating bias are related to SEB by the model. It is shown that the model predicts a decrease in the SEB susceptibility with a decrease in the internal base resistance (in the power BJT or parasitic BJT in the power MOSFET structure), a decrease in the operating bias, or an increase in the ambient device temperature. These findings are then qualitatively verified with experimental data.

Fast neutron irradiation tests were performed to determine the correlation of change of drain-source resistance and neutron fluence for power MOSFETs. The Objectives of the tests were: (1) to detect and measure the degradation of critical MOSFET device parameters as a function of neutron fluence (2) to compare the experimental results and the theoretical model. In general, the drain-source resistance increased from 1 Ohm to 100 Ohm after exposure to fast neutron fluence of 3 x 1014 neut/cm2, and decreased by a factor of five after high temperature annealing.

Many high performance amplifiers use power MOSFETs in their output stages, especially in operational amplifier applications whenever high current or power is needed. MOSFETs have advantages over bipolar transistors in amplifier output stage because MOSFETs are majority carrier devices. The result is wide frequency response, fast switching and better linearity than power bipolar transistors. But unlike bipolar circuits, which are relatively tolerant of ionizing radiation, MOSFETs may suffer severe parametric degradation at low total-dose levels. The effects of ionizing radiation on MOSFETs are discussed, and the performance of an amplifier circuit that uses a complementary MOSFET source follower in its output stage is simulated to examine the effect of MOSFET radiation damage on amplifier performance. An increase in power dissipation was the most significant degradation caused by ionizing radiation.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Cressler, John; Committee Member: Citrin, David; Committee Member: Shen, Shyh-Chiang. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

Application of power MOSFETs in spaceborne power converters was simulated by exposing devices to low-dose-rate ionizing radiation. Both radiation-hardened and nonhardened devices were tested with constant and switched gate biases during irradiation. In addition, some of the devices were under load. The threshold-voltage shifts were strongly bias dependent. The threshold-voltage shift of the nonhardened parts was approximately dose-rate independent, while the hardened parts exhibited significant dose-rate dependence. A pre-anneal dose-rate dependence was found for the interface-state buildup of the switched and positively biased devices, but the results for the switched devices were qualitatively different than those for the positively biased devices. The buildup of interface trapped charge was found to be the primary contributor to mobility degradation, which results in reduced drive capability and slower operation of the devices. These results indicate that new methods need to be utilized to accurately predict the performance of power MOSFETs in space environments.

A summary of total dose effects observe in advanced Silicon Germanium (SiGe) Heterojunction Bipolar Transistors (HBTs) is presented in this work. The principal driving froces behin the increased use of SiGe BiCMOS technology in space based electronics systems are outlined in the motivation Section of Chapter I. This is followed by a discussion of the strained layer Si/SiGe material structure and relevant fabrication techniques used in the development of the first generation of this technology. A comprehensive description of the device performance is presented. Chapter II presents an overview of radiation physics as it applies to microelectronic devices. Several sources of radiation are discussed including the environments encountered by satellites in different orbital paths around the earth. The particle types, interaction mechanisms and damage nomenclature are described. Proton irradiation experiments to analyze worst case displacement and ionization damage are examined in chapter III. A description of the test conditions is first presented, followed by the experimental results on the observed dc and ac transistor performance metrics with incident radiation. The impact of the collector doping level on the degradation is discussed. In a similar fashion, gamma irradiation experiments to focus on ionization only effects are presented in chapter IV. The experimental design and dc results are first presented, followed by a comparison of degradation under proton irradiation. Additional proton dose rate experiments conducted to further investigate observed differences between proton and gamma results are presented.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology. / Front-end power converters for nanosatellite applications demand better performance in accurate reference tracking because of the wide-range input voltage of the solar panels. The very tight output voltage requirements demand a robust, reliable, and high-efficiency converter. The control of such a converter is very complex and time consuming to design. Two commonly used control modes are current and voltage control. The design and implementation of a voltage controller for DC–DC power converter is simpler but compared to current mode controller, does not do provide for overcurrent protection. A single-ended primary inductance converter (SEPIC) was selected for this research work because of its ability to buck or boost the input voltage coupled with the ability to provide noninverting polarity with respect to the input voltage. Parameter values for the converter studied are used to analyse and design both the voltage and the current mode controllers for the nanosatellite front-end power converter. Output voltage reference tracking with step and ramp changes in the input voltage is evaluated in terms of the time taken to reach steady-state after the induced disturbances and either the overshoot or undershoot of the output voltage reference. The design of analogue pulse width modulation (PWM) study was carried out in order to drive the metal-oxide-semiconductor field-effect transistor (MOSFET) switch. For the two controllers, changes in the reference output voltage in response to load changes are also studied. An examination of the effects of solar radiation on the MOSFET switch was conducted; this switch is the main component of the front-end DC–DC power converter for a nanosatellite. At the more general level the examination also provided information on the response of the semiconductor technology in space application. The overall purpose of studying the MOSFET switch was to investigate the mechanisms that will facilitate its ability of switching ‘on’ and ‘off’ without failure as a result of solar radiation. The effects of solar radiation on MOSFET device in space, has resulted in more malfunctions of these devices in the past five years than over the preceding 40 years.

Extreme environment applications impose stringent demands on technology platforms that are incorporated in electronic systems. Space is a classic extreme environment, encompassing both large temperature fluctuations as well as intense radiation fields. Silicon-germanium technology has emerged as a competitive platform for space-based applications, owing to its excellent low-temperature performance and total ionizing dose tolerance. This technology has however been repeatedly shown to be vulnerable to single event phenomena induced by galactic cosmic rays as well as trapped particles within the earth's geomagnetic field. To improve the radiation tolerance of systems incorporating SiGe components, modifications to fabrications steps (Radiation Hardening by Process, RHBP) and/or device/circuit topologies (Radiation Hardening by Design, RHBD) may be employed. For this thesis, two methodologies are analyzed, both RHBD techniques which come at no additional power/area penalty for implementation.