The industrial revolution started with the invention of the steam engine and
the loom. Two hundred years later, the invention of the first transistor in
1947, marked the beginning of the so-called second industrial revolution. The
device was smaller, faster, more powerful, and had a longer lifetime than the
tubes. For the invention of the bipolar transistor three researchers of the
Bell Laboratories, namely William Shockley, John Bardeen, and Walter Brattain,
were awarded a Nobel Price in 1956.
After the transistor had been invented, it was still necessary to solder the
different parts of electronic circuits together. Jack Kilby of Texas
Instruments was the first person to realize that the different components in a
circuit could be integrated on a single piece of silicon. The successful
laboratory demonstration of that first simple microchip in 1958, made history.
Microelectronics was born, one of the fastest developing industrial
branches today, with an annual turnover of more than 120 billion USD and
supporting electronic market of more than 1000 billion USD. Especially fast is
the market growth in the communications area (cellular phones, personal
communications systems, wireless local communications networks, electronic
traffic management). This is a driving driving force for the development of ever
faster ICs including super-fast transistors.
In 1957 Herbert Kroemer of RCA proposed the first heterostructure, device that
contains thin layers of different semiconductors stacked on top of each
other. His theoretical work showed that heterostructure devices could offer
superior performance compared with conventional transistors. In 1963 Herbert
Kroemer and Zhores Alferov of the Ioffe Institute in Russia independently
proposed ideas to build semiconductor lasers from heterostructure
devices. Alferov built the first semiconductor laser from gallium arsenide and
aluminium arsenide in 1969.
This year's Nobel Prize in Physics has been awarded to Kilby "for his part in
the invention of the integrated circuits", and to Kroemer and Alferov "for
developing semiconductor heterostructures used in high-speed- and
The Heterojunction Bipolar Transistors (HBTs) are among the most advanced
semiconductor devices. They match well today's requirements for high-speed
operation, low power consumption, high-integration, low cost in large
quantities, and operation capabilities in the frequency range from 0.9 to
100 GHz. For example, III-V semiconductor group devices and circuits were
always known by their high speed, but also by their expensive production and
lower integration, compared to the silicon-based ones. Today, with III-V
heterojunction MMICs in mass production on six-inch wafers in quantities 10
million and above, this is no longer a concern for the gallium-arsenide based
HBTs. The silicon bipolar junction transistors (BJTs) have the benefits of the
silicon technology, e.g. the high integration and low-cost production, but are
restricted to lower frequencies. Important steps forward to faster
silicon-based devices were the invention of the polysilicon emitter transistor
and the silicon-germanium HBT, which are competitive in terms of speed to the
To cope with the explosive development costs of today's semiconductor industry
Computer-Aided Design (CAD) methodologies are extensively used. Electronic CAD
(ECAD) is concerned with the design of ICs above the device level. Technology
CAD (TCAD) is devoted to the simulation of the fabrication process and
operation behavior of a single or a small number of devices. Technology,
device, and circuit simulation tools save expensive experimental efforts to
obtain significant improvements of the device performance.
MINIMOS-NT is a two-dimensional device/circuit simulator used in the VISTA TCAD framework.
A large part of the work presented in this thesis is on the development and the
practical application of MINIMOS-NT.
The status of research regarding HBTs will be presented in Chapter 2. It
includes a review of state-of-the-art devices, a discussion on the materials and
material systems on which HBTs are based on, and a review of state-of-the-art
device simulators, including MINIMOS-NT.
In Chapter 3 the physical modeling in MINIMOS-NT is presented. It contains models
for the lattice, thermal, and transport properties of various semiconductor
materials, as well as models for several important effects taking place in
Chapter 4 contains the simulation results for several different types of
GaAs-based and Si-based HBTs demonstrating the extended capabilities of
MINIMOS-NT. Most of the results are verified against experimental data. The
chapter also includes investigations which confirm the usefulness of device
simulation for practical applications.
A summary and outlook conclude this work in Chapter 5.