Optical Science and Engineering ETDs

Publication Date

Fall 12-2022

Abstract

The creation of a laser cooled semiconductor device has been a long sought achievement. GaAs-based devices have emerged as a promising candidate for the realization of this goal. Efforts to improve the efficiency of such devices have enabled the material to exhibit external quantum efficiencies (EQE, a measure of the probability that an excitation leads to the emission of a photon) of 99.5\%. Despite this impressive feat, a laser coolable device remains elusive.

To investigate the obstacles to such a device, the material characteristics of GaAs-based double heterostructures (DHS) are theoretically and experimentally examined. Through this study, a GaAs $\vert$ AlGaAs DHS is shown to achieve an EQE performance equivalent to state-of-the-art GaAs $\vert$ GaInP DHS (the 99.5\% EQE device) for the first time. Additionally, this structure exhibits a lower parasitic background absorption (PBA), heat-inducing absorption of a pump laser, than that attainable in current GaAs $\vert$ GaInP DHS. Thus this sample represents the current state-of-the-art for GaAs DHS. This result was enabled by a supporting study into semiconductor growth techniques. Specifically, metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were compared, finding MBE-grown structures had an order of magnitude smaller parasitic background absorption (PBA) than those grown with MOCVD. Furthermore, the PBA contributions for individual layers of these GaAs DHS is reported for the first time using a novel thermal lens technique. The passivation layers are identified as the dominant contributors at 1020-1070~nm, with the GaAs layer the primary contributor in the Urbach tail. Thus, a future investigation into, and improvement upon, the sources of PBA within these layers is necessary to the optical refrigeration of a semiconductor device.

Degree Name

Optical Science and Engineering

Level of Degree

Doctoral

Department Name

Optical Science and Engineering

First Committee Member (Chair)

Mansoor Sheik-Bahae

Second Committee Member

Kevin J. Malloy

Third Committee Member

Denis Seletskiy

Fourth Committee Member

Tito Busani

Keywords

GaAs DHS Optical Refrigeration EQE

Document Type

Dissertation

Language

English

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