The focus of this thesis is the investigation of thin-film transistors (TFTs) based on amorphous oxide semiconductors (AOSs) in two circuit applications. To date, circuits implemented with AOS-based TFTs have been primarily enhancement-enhancement inverters, ring oscillators based on these inverters operating at peak frequencies up to ~400 kHz, and two-transistor...
The objective of this thesis is to contribute to the development of p-type materials for transparent electronics applications. Thin films of ®-BaCu2S2, a p-type semi-transparent semiconductor, are fabricated and characterized. ®-BaCu2S2 has a transmittance of 60% to 80 % in the visible portion of the electromagnetic spectrum. The mobility, conductivity,...
The focus of this thesis involves development of highly transparent, n-channel, accumulation- mode thin-film transistors employing a zinc tin oxide (ZTO) channel layer. ZTO-based transparent thin-film transistors (TTFTs) show improved device performance compared to ZnO-based TTFTs. An estimated peak effective mobility for these devices as high as ~100 cm² V⁻¹sec⁻¹...
Alternating-current thin-film electroluminescent (ACTFEL) devices are used in the
formation of pixels in flat panel displays. ACTFEL flat panel displays have many
advantages over other flat panel technologies. Specifically, ACTFEL panels are emissive
displays, they have high brightness, wide viewing angles, and rugged construction.
Although much is already known about...
The objective of this thesis is to provide an initial demonstration of the feasibility of constructing highly transparent active electronic devices. Such a demonstration is successfully achieved in the fabrication of ZnO-based thin film transistors (TFTs) exhibiting transparency greater than ~90% in the visible portion of the electromagnetic spectrum and...
The objective of the work reported herein is to explore the impact of decreasing channel thickness on radio-frequency (RF) sputtered amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) electrical performance through the evaluation of drain current versus gate voltage (I[subscript D] − V[subscript G]) transfer curves. For a fixed set of...
White electroluminescence (EL) was observed for the
first time from diamond-like carbon (DLC) films at room
temperature. Electroluminescence was observed by the
application of ac voltages in excess of 200 V to a metal-insulator-
semiconductor (i.e. DLC)-insulator-metal (MISIM)
device structure.
For EL applications, three types of the DLC films were...
A study of deep levels of the emitter region of a
heterojunction bipolar transistor is investigated using deep
level transient spectroscopy (DLTS), deep level admittance
spectroscopy (DLAS), thermally stimulated capacitance
(TSCAP), and capacitance-voltage (C-V) profiling. The DX
center, with an activation energy of 0.45 eV, is the only
deep level...
Amorphous oxide semiconductors (AOSs) are of great current interest for thin-film transistor (TFT) channel layer applications. In particular, indium gallium zinc oxide (IGZO) is under intense development for commercial applications because of its demonstrated high performance at low processing temperatures. The objective of the research presented in this thesis is...
The primary focus of this thesis involves modeling and development of p-type thin-film transistors (p-TFTs), moving towards the realization of a filly transparent thin-film transistor (TTFT). The modeling portion of this thesis emphasizes the development of physics-based TFT models, specifically focusing on the elucidation of non-ideal current-voltage characteristic behavior. A...
A class of high-performance thin-film transistor (TFT) channel materials has emerged
involving oxides composed of heavy-metal cations (HMCs) with (n-1)d¹⁰ns⁰ (n≥4)
electronic configurations. This thesis is devoted to the pursuit of three topics involving
the development of these materials for TFT applications: modeling TFT currentvoltage
characteristics, an exploratory method for...
The research presented herein represents an effort to combine the ultra-smooth surface of an amorphous metal thin film (AMTF) with a solution-processed dielectric synthesized via prompt inorganic condensation (PIC). Analysis of dielectric film quality is carried out via electrical measurements of metal-insulator-metal (MIM) diodes. Anneals at 500 and 700 °C...
Hot carrier effects in sub-micron lightly doped drain (LDD) n-channel
MOSFETs under static (DC) stress are studied in order to establish the degradation
mechanisms of such devices. Degradation is monitored as a function of time at various
gate voltages. Under accelerated aging conditions (i.e. large drain voltages) the gate
voltage...
Amorphous metal thin films (AMTFs) are of potential use for metal-insulator-metal (MIM) tunnel diode applications due to their ultra-smooth surfaces, a consequence of their amorphous microstructure. The objective of this thesis is to design a thermally-stable AMTF capable of maintaining MIM tunnel diode performance after a post-deposition anneal in excess...
A discrete trap model is developed and employed for elucidation of thin-film transistor (TFT) device physics trends. An attractive feature of this model is that only two model parameters are required, the trap energy depth, E[subscript T], and the trap density, N[subscript T]. The most relevant trends occur when E[subscript...
The aim of the research undertaken for this thesis was to develop a new high-performance amorphous oxide semiconductor (AOS) for use as a channel layer in a thin-film transistor (TFT). AOS TFTs offer higher electron mobility than the established amorphous silicon based technology. A new channel material comprised of aluminum...
The long-term goal of the research project initiated with this thesis is the development of lead-free, fully-transparent ferroelectric devices, such as ferroelectric capacitors or ferroelectric-gate field-effect transistors. Ferroelectric materials exhibit spontaneous polarization with the application of an external electric field, which is persistent upon removal of the applied field, and...
This thesis focuses on two aspects of oxide-based thin-film transistors (TFTs), contact resistance and instability assessment.
First, determination of the contact resistance of indium tin oxide (ITO) on two wide-band gap semiconductors, zinc oxide (ZnO) and indium gallium oxide (IGO), is attempted and the effects of contact resistance on device...
The achievements of this thesis are the development of several models for the SPICE (Simulation Program with Integrated Circuit Emphasis) simulation of alternating-current thin-film electroluminescent (ACTFEL) devices, organic light-emitting devices (OLEDs), and polymer light-emitting devices (PLEDs). First, an ACTFEL model based on the built-in HSPICE Fowler-Nordheim tunneling diode is developed,...
The goal of this thesis study is to develop an activated reactive evaporation (ARE) system and to demonstrate its utility by fabricating-alternating current thin-film electroluminescent (ACTFEL) oxide phosphor devices. ARE entails evaporation in an activated gas. The main ARE system components are three thermal evaporation sources, a microwave power supply,...
The primary objective of this thesis is to explore new absorber and p-type window layer materials for thin-film solar cell applications. A new thin-film electron beam deposition system has been installed, is now operational, and has been used to deposit several types of solar cell absorber layers. Material investigations include...
The central focus of this thesis is the design, fabrication and characterization of amorphous oxide semiconductor (AOS) thin-film transistor (TFT) current mirrors. The thin-film deposition and circuit fabrication methods used to realize zinc tin oxide (ZTO) TFT
current mirrors are addressed in order to elucidate the processing challenges for this...