We have developed a new floating-gate silicon MOS transistor for analog learning applications. The memory storage is nonvolatile; hot-electron injection and electron tunneling permit bidirectional memory updates. Because these updates depend on both the stored memory value and the transistor terminal voltages, the synapse can implement a learning function. We have derived a memory -update rule from the physics of the tunneling and injection processes, and have investigated synapse learning in a prototype array. Unlike conventional EEPROM devices, the synapse allows simultaneous memory reading and writing. Synapse transistor arrays can therefore compute both the array output, and local memory updates, in parallel. The synapse is small, and typically is operated at subthreshold current levels; it will permit the development of dense, low-power silicon learning systems.

Monte Carlo simulations of electron transport in seven semiconductors of the diamond and zinc-blende structure (Ge, Si, GaAs, InP, AIAs, InAs, Gap) and some of their alloys (AI,Ga,-xAs, In,Ga,-,As, Ga,In,- rP), and hole transport in Si have been performed at two lattice temperatures (77 and 300 K). The model employs band structures obtained from local empirical pseudopotential calculations and particle-lattice scattering rates computed from the Fermi Golden Rule accounting for band-structure effects. Intervalley deformation potentials significantly tower than those previously reported in the Monte Carlo literature are needed to reproduce available experimental data. This is attributed to the more complicated band structures we have adopted, particularly around the L- and X-symmetry points in most materials. Despite the satisfactory agreement obtained between Monte Carlo results and some experiments, the inconsistency or lack of experimental information regarding the hand structure ( AIAs, Gap, InP), velocity-field characteristics (Gap, InAs, Al,Ga,-,As, Ga,In, ~ rP), and impact ionization coefficients (InAs) of many materials indicate that a significant uncertainty still remains in our ability to describe the charge transport in many of these technologically significant materials.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1. Water Vapor Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2. DIAL Technique for Measuring Water Vapor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Lidar Atmospheric Sensing Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 2.2. DIAL Detection System Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 3. Avalan...

This memorandum reviews the theory of thermoelectric cooling. Also, the design and performance of a proportional integral (PI) temperature controller and its application to an EG&G APD package (C30649E), which includes a built-in TEC and a thermistor, are discussed. This APD package was chosen, after characterizing a group of APDs, in order to develop an advanced detection system for atmospheric water vapor DIAL measurements (ref. 2, 4, 5 and 6).

ADVANCED ATMOSPHERIC WATER VAPOR DIAL DETECTION SYSTEM Measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a powerful method to perform such measurement from aircraft and space. This thesis describes a new advanced detection system, which incorporates major improvements regarding sensitivity and size. These improvements include a low noise advanced avalanche photodiode detector, a custom analog circuit, a 14-bit digitizer, a microcontroller for on board averaging and finally a fast computer interface. This thesis describes the design and validation of this new water vapor DIAL detection system which was integrated onto a small Printed Circuit Board (PCB) with minimal weight and power consumption. Comparing its measurements to an existing DIAL system for aerosol and water vapor profiling validated the detection system. ii iii TABLE OF CONTENTS Page LIST OF...

A one-dimensional (1-D) steady state drift-diffusion device model that incorporates impact ionisation has been developed for the simulation of avalanche photodiodes. The model uses finite difference analysis to solve the time independent semiconductor equations across a user specified structure. The model includes DC illumination, allowing wavelength dependent effects to be modelled. The effect of neutron radiation damage is included via the introduction of deep acceptor levels subject to Shockley-Read-Hall statistics. Preliminary analysis of an EG&G reverse APD structure has been performed.