Molecular beam epitaxy growth of indium nitride and indium gallium nitride materials for photovoltaic applications

InGaN;Mg doping;III-Nitrides;Photovoltaics;Molecular beam epitaxy

Trybus, Elaissa Lee ; Electrical and Computer Engineering

University:Georgia Institute of Technology

Department:Electrical and Computer Engineering

关键词: InGaN;    Mg doping;    III-Nitrides;    Photovoltaics;    Molecular beam epitaxy;   

Others  :  https://smartech.gatech.edu/bitstream/1853/28108/1/trybus_elaissa_l_200905_phd.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

The objective of the proposed research is to establish the technology for material growth by molecular beam epitaxy (MBE) and fabrication of indium gallium nitride/gallium nitride (InxGa1-xN/GaN) heterojunction solar cells.InxGa1-xN solar cell have the potential to span 90% of the solar spectrum, however there has been no success with high indium (In) incorporation and only limited success with low In incorporation InxGa1-xN.Therefore, this present work focuses on 15 - 30% In incorporation leading to a bandgap value of 2.3 - 2.8 eV.This work will exploit the revision of the indium nitride (InN) bandgap value of 0.68 eV, which expands the range of the optical emission of nitride-based devices from ultraviolet to near infrared regions, by developing transparent InxGa1-xN solar cells outside the visible spectrum.Photovoltaic devices with a bandgap greater than 2.0 eV are attractive because over half the available power in the solar spectrum is above the photon energy of 2.0 eV.The ability of InxGa1-xN materials to optimally span the solar spectrum offers a tantalizing solution for high-efficiency photovoltaics.Using the metal modulated epitaxy (MME) technique in a new, ultra-clean refurbished MBE system, an innovative growth regime is established where In and Ga phase separation is diminished by increasing the growth rate for InxGa1-xN.The MME technique modulates the metal shutters with a fixed duty cycle while maintaining a constant nitrogen flux and proves effective for improving crystal quality and p-type doping.We demonstrate the ability to repeatedly grow high hole concentration Mg-doped GaN films using the MME technique.The highest hole concentration obtained is equal to 4.26 e19 cm-3, resistivity of 0.5 Ω-cm, and mobility of 0.28 cm2/V-s.We have achieved hole concentrations significantly higher than recorded in the literature, proving that our growth parameters and the MME technique is feasible, repeatable, and beneficial.The high hole concentration p-GaN is used as the emitter in our InxGa1-xN solar cell devices.