Two significant drivers to innovation in electronics and electronic materials in recent
history have been electronic device scaling and the pursuit of high efficiency photovoltaic
cells at low costs. The motivations of these two fields have been interestingly parallel, as
“density” has been a key metric for both – areal energy density in the case of photovoltaics,
and component density in the case of electronic devices. So strong is this motivation to
lower device costs by packing more performance into a smaller area that “laws” have been
devised to inspire innovation in each field, with Moore’s law to describe the periodic
doubling of transistor density and Swanson’s law to outline the steady drop in solar cell
module costs over time. As each law approaches a wall erected by fundamental physical
limitations, science must identify roadblocks and solutions that can allow innovation to
continue.
Semiconductor materials are a key limiting factor for each application, as their physical
properties determine ultimate functionality of a device and the challenges involved in
device design. In both electronic and optoelectronic applications, scalable manufacturing
of III-V materials has been a promising avenue to improvement, as while they are
traditionally expensive to produce, they use a larger portion of the solar spectrum for
photovoltaic devices, and are easily utilized in the fabrication of high performance optical
and electronic devices. In recent years, a more scalable method for the growth of III-V
materials without costly epitaxial substrates has been developed, by utilizing the vaporliquid-
solid growth (VLS) process to grow structures confined by a metal catalyst.
Structures such has nanowires have been fabricated with this technique and studied
extensively, but a recent expansion of the approach has also allowed for growth of highquality
thin films using planar templates for nucleation control. In this dissertation, I
discuss the use of this approach in a number of applications, including the development
of large-area photovoltaic devices and an evolution of the technique to greatly expand its
application space through lower process temperatures.
First, I will discuss an ideal preliminary application of this technique, with the
development of p-body InP photoelectrochemical cells for the direct production of
chemical fuel using sunlight. This application shows the utility of large-scale
polycrystalline growth with larger than normal grain sizes enabled by the technique, and
the fundamentals of the growth process and usable doping methods are explored in
tandem. This study also demonstrates the successful application of an efficient selective
electron contact to the poly-InP system, enabling promising device performance and
enhancing device stability under harsh photocathode operation conditions. Hydrogen
fuel production from simulated sunlight is also directly and quantifiably observed from
the device as a capstone to this experiment.
Following the investigation of larger area thin-film growth, the microscale templatedliquid-
phase (TLP) crystal growth method is explored and expanded to target a wider
range of applications. This method, a modification to the thin-film vapor-liquid solid (TFVLS)
process initially studied, has previously enabled growth of defined patterns of single
crystal domains on amorphous substrates. While this is an impressive result with great
promise for integration of III-Vs into highly scaled electronics, growth temperatures
previously explored would need to be lowered significantly for facile integration to be a
reality. Using a simple modification to the existing TLP process, I demonstrate growth
temperatures well within the silicon CMOS thermal budget, with proof-of-concept devices
fabricated at temperatures as low as 270ºC with the InP system. With applicability to a
variety of substrates, this study has neatly expanded the application space of III-Vs, with
complex methods and material requirements replaced with simple direct growth.
