The research presented herein focuses on electrical assessment of oxide thin films as insulators. The current density-electric field (J-E) characteristics of four insulators of dramatically different electrical quality are assessed in terms of their operative electronic conduction mechanisms. Conduction in the two high-quality insulators is dominated by Ohmic conduction and...
The trend towards higher resolution, faster refresh rate active-matrix liquid-crystal displays (AMLCDs) as well as the emergence of active-matrix organic light-emitting diode (AMOLED) displays is driving the demand for amorphous oxide semiconductor thin-film transistors (AOS TFTs) with higher mobility. A physics-based model for carrier transport in an amorphous semiconductor is...
The electrical stability of amorphous indium-gallium-zinc oxide (a-IGZO) thinfilmtransistors (TFTs) is investigated for flat-panel display applications. Althoughproducts incorporating a-IGZO TFT backplanes are already commercially available,e.g., iMac with 5K retina display, technical challenges need to be addressed for nextgenerationapplications, e.g., active-matrix organic light-emitting diode displays.Device stability is one crucial issue. The...
CIGS and CdTe based commercial thin-film solar cells (TFSCs) require an absorber thickness greater than 2 µm and 4 µm, respectively, to adequately absorb the solar spectrum. To efficiently extract photoexcited electrons, these TFSCs require relatively defect-free absorbers with high-minority carrier mobility (> 100 cm2V−1s−1) and long lifetime (> 10...
Due to a lack of grain boundaries, an amorphous metal thin film (AMTF) possesses advantageous mechanical properties and enhanced chemical stability that is potentially useful for thermal inkjet (TIJ) printing applications. The use of an AMTF as a TIJ resistor or cavitation plate could lead to a thinner TIJ cavitation...
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...
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 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...
Current cadmium telluride and copper indium gallium diselenide thin-film solar cells
(TFSCs) utilize thick absorbers (2 - 4 μm). For efficient carrier extraction in these TFSCs,
the absorber layer requires high carrier mobilities and a long minority carrier lifetime, which
necessitates the use of a high purity, defect-free thin film....
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...
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...
The atomic solid state energy (SSE) scale is introduced as a tool for inorganic materials design. The SSE scale is obtained by assessing an average electron affinity (EA) (for a cation) or an average ionization potential (IP) (for an anion) for each atom using data from compounds having that specific...
The drain current of InP MISPETs is often observed
to decrease as a function of time after the application of
a positive gate bias which involves an accumulation of
electrons in the channel. Various models have been
proposed for this drain current drift (DCD) phenomenon.
In this thesis, variable-temperature bias-stress...
An analytical expression is derived which allows the
bulk minority carrier recombination lifetime, t, and the
surface recombination velocity, S, to be extracted from a
single noncontact photoconductivity decay (PCD) measurement. This analytical expression is rather complex, but
can be reduced to a first order approximation. The first
order approximation...
The stability of ZnS:Mn AC thin film Electroluminescence (ACEFEL)
devices as demonstrated by the brightness-voltage (BV)
characteristics is discussed. Two procedures for improvement of the
stability are demonstrated. The first method is the addition of a
CaS buffer layer to one or both interfaces of the ZnS active phosphor
layer....
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...
In this thesis the concept of inhomogeneous
dielectrics is demonstrated for various optical coating
applications. Compositionally-varying silicon oxynitride
(SiON) dielectric layers, with the refractive index
varying as a function of position, are grown by computer-controlled
plasma-enhanced chemical vapor deposition
(PECVD) using silane, nitrogen, and nitrous oxide reactant
gases. Compositionally graded...
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...
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...
The accomplishments presented in this thesis are the development of three models
for simulation of space charge generation in the phosphor layer of alternating current
thin-film electroluminescent (ACTFEL) devices and the results from simulation
of these models. First, a single sheet charge model is developed and simulated.
The single sheet...
The goal of this thesis is to identify and to explore novel ACTFEL phosphor
materials. Several important materials properties relevant to ACTFEL phosphor
development are identified. All of these properties cannot be obtained simultaneously.
Therefore, several key phosphor materials properties are identified as critical to the
development of an ACTFEL...
Fabrication techniques and process integration considerations for amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) constitute the central theme of this dissertation. Within this theme three primary areas of focus are pursued.
The first focus involves formulating a general framework for assessing passivation. Avoiding formation of an undesirable backside accumulation layer...
An active-matrix electroluminescent (AMEL) design tool has been developed for
the simulation of AMEL display devices. The AMEL design tool is a software package
that simulates AMEL device operation using a lumped parameter circuit model. The
lumped parameter circuit model is developed primarily to address AMEL power
dissipation issues. The...
The goal of this thesis is the identification and synthesis of high-luminance,
primary color alternating-current thin-film electroluminescent (ACTFEL) devices.
Special attention is paid to the synthesis of primary color green ACTFEL devices because
of the lack of an adequate primary green ACTFEL phosphor and the dominance
of green wavelengths in...
In this thesis steady-state (i.e. steady-state with respect to the applied voltage waveform) transient current-transient voltage [i(t)-v(t)], transient brightness-transient current [b(t)-i(t)], transient brightness-transient voltage [b(t)-v(t)], transient current [i(t)], transient brightness [b(t)], and detrapped charge analysis are introduced as novel organic light emitting device (OLED) characterization methods. These analysis methods involve...
The main achievement of this thesis is the development of a two-sheet charge simulation model with space charge creation by trap-to-band impact ionization to describe the electrical characteristics of alternating-current thin-film electroluminescent (ACTFEL) devices. The two-sheet charge model localizes all of the space charge in the phosphor region of an...
The purpose of this thesis is to contribute to the understanding of SrS-based alternating-current thin-film electroluminescent (ACTFEL) device operation. Three main accomplishments serving this purpose are presented in this thesis. First, two new methods are developed for estimation of insulator capacitance in ACTFEL devices possessing a large amount of dynamic...
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 objective of the research presented in this thesis is to develop, implement, and demonstrate the utility of an n-sheet, state-space alternating-current thin-film electroluminescent (ACTFEL) device model. In this model, the phosphor layer is discretized into n + 1 layers, with band-to-band impact ionization, space charge creation/ annihilation, and luminescent...
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...
Current leading thin-film solar cell technologies, i.e., cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS), employ elements which are either toxic (Cd), or rare and/or expensive (In, Te, Ga, and Cd). The aim of this thesis is to investigate new, abundant, non-toxic p-type semiconductors for potential solar absorber application....
Indium-gallium-zinc oxide (IGZO) and zinc-tin oxide (ZTO) are investigated for thin-film transistor (TFT) applications. Negative bias illumination stress (NBIS) is employed for electrical stability assessment. Unpassivated IGZO and ZTO TFTs suffer from severe NBIS instabilities. Zinc-tin-silicon oxide is found to be an effective passivation layer for IGZO and ZTO TFTs,...
The aim of this dissertation is to develop non-traditional approaches to alternating-current thin-film electroluminescent (ACTFEL) device fabrication. ACTFEL technology suffers from a lack of adequately bright and efficient primary-color phosphors and cannot presently compete in the low-cost display market. Therefore the research presented in this dissertation focuses on an exploration...