Gallium phosphide (GaP), with its wide band gap of 2.26 eV, is a good candidate for the top junction solar cell in a multijunction solar cell system. Here, we design, fabricate, characterize, and analyze GaP solar cells. Liquid phase epitaxy is used to grow the semiconductor layers. Four generations of GaP solar cells are developed and fabricated with each solar cell structure being designed and improved based on the first principles analyses of the predecessor solar cells. Quantum efficiency and current-voltage measurements are used to analyze the solar cell performance and to develop predictive models. We create a GaP solar cell with an efficiency of 2.42% under AM 1.5G one sun illumination.

Wide Band Gap Gallium Phosphide Solar Cells

Heterojunction and superlattice detectors for infrared to ultraviolet

A good candidate for the top junction cell in a multi-junction solar cell system is the GaP solar cell because of its proper wide band gap. Here, for the first time, we passivate the front surface of these GaP solar cells with an AlGaP layer. To study the passivation effect of this layer, we design a novel growth procedure via liquid phase epitaxy. X-Ray diffraction results show that the resulting passivation epitaxial layer is of good quality. Integrated quantum efficiency measurements show an 18% increase in current due to the AlGaP. The current-voltage measurements indicate that with this AlGaP surface passivation layer, the GaP solar cell's efficiency is 2.90%. This is an improvement over previously reported results for GaP solar cells.

Improving GaP Solar Cell Performance by Passivating the Surface Using AlxGa1-xP Epi-Layer

Publisher Summary Infrared (IR) radiation was discovered accidently by Sir Frederick WilliamHerschel (1738–1822. The Second World War dramatically increased the interest in IR detection in which photon detectors were developed to improve the performance. Now the infrared detectors are used in various sectors not only in defense and security, but also in manufacturing, medicine, environment, and various other testing/monitoring applications. This chapter focuses on detection using internal photoemission across an interfacial workfunction in a semiconductor homo- or heterojunction architecture. Although quantum well structures also have a junction and an interface, the energy difference between the two states associated with the transitions are because of the quantization effects in the well material but not at an interface. The detector concepts discussed in the chapter can be applied to any semiconductor material where an interface can be formed. Varying the interfacial workfunction leads to different energy photons to be detected giving rise to different threshold wavelength (λ t ) detectors. The chapter also discusses the way multiband detection is achieved in a single detector element. It also discusses the concept of controlling the operating temperature and responsivity by adjusting the interfacial workfunction in connection with the spin-orbit split-off detectors.

Homo- and Heterojunction Interfacial Workfunction Internal Photo-Emission Detectors from UV to IR

Structural, electronic and optical properties of the zinc-blende Ga1−x Al x P ternary alloys with their ordered AlP and GaP binary compounds have been investigated, using the full potential linearized augmented plane wave method in conjunction with the density functional theory. The total energies are carried out to calculate the lattice constant, bulk modulus and its pressure derivative of the zinc-blende AlP, GaP binary compounds and their corresponding ternary Ga1−x Al x P solid solutions for the compositions (x = 0.25, 0.50 and 0.75). The band gap energies and the optical properties of these materials are investigated at normal pressure condition as well as under high pressure levels. The estimated results obtained from this work are justified, discussed and compared with the experimental data and other available theoretical works.

http://iopscience.iop.org/article/10.1088/2053-1591/2/10/105904/pdf

V.M. Andreev

Papers

GaP-AlGaP heterojunction photosensors with photosensitivity maximum at 380–420 nm