5.4.1 Introduction to III-V Nitrides - Growth Methods - Introduction
The first major efforts to grow high quality III-Nitride semiconductors
were conducted in the 1960's and 1970's. One of the most popular thin film
growth techniques for early III-Nitride growth was reactive sputtering,
although all sputtered material was at best polycrystalline. The next major
step forward was the use of CVD techniques, and it proved to be possible
to grow single crystalline GaN. The biggest problems encountered were,
and still are, the lack of suitable lattice matched substrate materials
as well as what is thought to be incomplete nitrogen incorporation resulting
in high n-type background carrier concentrations in GaN and InN.
Early doping attempts to achieve p-type material failed. Although
no device grade material was obtained, much was learned about the properties
of III-Nitride semiconductors.
Improved crystal growth techniques, mostly due to MBE and MOVPE developed
during the 1980's, refocused the efforts to produce high quality material.
As a result the n-type background carrier concentration was improved
dramatically to as little as 4x10^15 cm^-3 and p-type GaN was produced
using dopants. Zinc-Blende polytypes of GaN, AlN, and InN have been grown
on suitable substrates as well as AlGaN/GaN heterostructures.
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