Abstract:
ZnO is a wide band gap (~3.3 eV) semiconductor at room temperature with high
excitation binding energy (~60 meV) making it extremely attractive in many optoelectronic
applications, e.g., light emitting diodes (LEDs), laser diodes (LDs), transparent
semiconductors, and photovoltaic [1-2]. Compared to GaN, which is already in application,
ZnO is significantly cheaper and offers alternatives to overcome the cost associated with GaN
technology [2]. GaN is the most important semiconductor after silicon [3]. The market of
lighting industry will be amount to 120 billion by 2020 [4]. This huge lighting industry can
be accessible if ZnO based technology can be realized. However, stable p-doping remains
elusive in this system, thus hindering its application in bi-polar devices [5]. Extensive
research is being pursued to understand the problem and overcome the difficulty. The first
part of this thesis is directed towards this challenge by one of the several approaches already
proposed in the literature i.e. by pushing the valence band upwards towards the vacuum level
and at the same time understanding the role of native defects their role and control in this
system. We have grown epitaxial forM.S. of ZnO films so that any success can be translated
immediately to device fabrication stage.
