Date of Award

Fall 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Engineering (DEng)

Department

Electrical Engineering (ENAS)

First Advisor

Han, Jung

Abstract

The Short-Wave Infrared (SWIR) range is a crucial wavelength window with a wide range of applications. Just to name a few, it covers the important telecommunication bands, provides advantages in bio-sensing and there are emerging applications recently such as noninvasive glucose monitoring, eye-safe 3D sensing and Si photonics. The development of SWIR vertical cavity surface emitting lasers (VCSELs) has been ongoing for more than 30 years but has not yet led to commercialization. The main reason is that it hasn't been easy to build highly reflective distributed Bragg reflectors (DBRs). Unlike the GaAs systems, materials lattice-matched to InP suffers from small refractive index contrast or brings difficulty in epitaxy.In this thesis we will demonstrate the usage of nanoporous (NP) InP to break the bottleneck towards manufacturable SWIR VCSELs. This is achieved by the conductivity selective electrochemical (EC) etching of n-InP. The porosification of InP provides tunability in the refractive index and the index contrast (Δn) between NP InP and solid InP can be as high as 1. After the initial EC etching test, we built highly reflective NP InP DBRs and performed a proof-of-concept demonstration of NP InP VCSEL. Room temperature (RT) continuous wave (CW) single mode operation was achieved for both 1,380 nm and 1,550 nm VCSELs with NP DBR. Afterwards, we performed a systematic study regarding the EC etching of InP. A phase diagram was built to map out the pore morphology. We also studied the thermal properties of NP InP. NP InP was found to be thermally stable up to 550°C in nitrogen ambient. During the development of NP InP VCSELs, we worked on refining fabrication processes, optimizing epitaxial structure, and addressing scalability challenges. The power conversion efficiency (PCE) was increased to more than 26% by improving the tunnel junction and the overlap between the optical mode and current injection. Based on these results, we believe that the NP InP technology will be the pathway to break the 30 years impasse towards manufacturable SWIR VCSELs and enable a variety of applications.

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