Abstract

The emergence of proliferated low-Earth orbit (pLEO) constellations using small satellites has resulted in significant interest in lowering the size, weight, and power (SWaP) of mission critical subsystems. III-V semiconductors are the class of materials typically used for photovoltaic (PV) arrays for satellites due to their exceptional efficiencies of upwards of 35 % and ability to be made thin, flexible, and lightweight. This is contrasted with the high SWaP communication system, which utilizes a radio frequency (RF) transceiver in order to communicate with a ground station. A lower SWaP alternative to the RF transceiver is to transmit data using free space optical (FSO) communication. FSO communication at 1.55 µm is of particular interest due to the wavelength being inherently eye safe and existing infrastructure from the telecommunications industry. This research presents on a hybrid power generation/data communication device using III-V PV as the power generating component and an InP-based multiple quantum well (MQW) electroabsorption modulator (EAM) targeted for operation at 1.55 µm as the data communication component. A MQW EAM utilizes the quantum confined Stark effect (QCSE) to shift the absorption coefficient of the material; using the QCSE amplitude modulation of a signal is possible over FSO communication. To be hybridized with a PV device, a surface normal EAM is required. While it is advantageous to have a large area to aid pointing accuracy with FSO communication, the EAM suffers from decreased bandwidth due to area-dominated capacitive effects. These capacitive effects were extensively studied, and data rates ranging from 0.25 to 1 Mbps were demonstrated. Additionally, in order to accurately target device operation at 1.55 µm, the thickness of the InGaAs quantum well region and the InAlAs barriers were investigated through both simulation and experimental work. Two device architectures were investigated; a four-terminal, mechanically bonded hybrid device and a three-terminal, monolithically integrated device. The four-terminal, mechanically bonded device allows growth of the PV device to be conducted on a GaAs substrate, enabling higher power conversion efficiencies compared to growth on InP. A dual junction InGaP/GaAs photovoltaic device with an AM0 power conversion efficiency of 23 % was mechanically bonded to an InP-based EAM in a 0.5 U form factor module. Using a segmented modulator design, a data rate for the module of 0.5 Mbps was demonstrated. The three-terminal device, all grown monolithically on InP, has the advantage of only requiring one growth and one fabrication. In addition, the monolithically integrated device further reduces the SWAP of the hybrid device by 50 % as only one substrate is required. This design required careful consideration of the shared contact layer between the PV device and EAM, needing to balance fractional power loss in the PV device and parasitic absorption of 1.55 µm light. A single junction InP PV device was grown a top of an InGaAs/InAlAs EAM, demonstrating simultaneous power generation and data transmission, and to our best knowledge demonstrated the first hybrid, monolithically integrated device to be successfully fabricated. These hybrid devices have applications that extend beyond satellites, such as unmanned aerial vehicles, orbital debris tagging, and implantable medical devices.

Library of Congress Subject Headings

Free space optical interconnects; Photovoltaic power generation; Metal organic chemical vapor deposition; Epitaxy

Publication Date

12-7-2023

Document Type

Dissertation

Student Type

Graduate

Degree Name

Microsystems Engineering (Ph.D.)

Department, Program, or Center

Microsystems Engineering

College

Kate Gleason College of Engineering

Advisor

Seth M. Hubbard

Advisor/Committee Member

Stephen J. Polly

Advisor/Committee Member

Raymond Hoheisel

Campus

RIT – Main Campus

Plan Codes

MCSE-PHD

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