Electrically conductive ZnO/GaN distributed Bragg reflectors grown by hybrid plasma-assisted molecular beam epitaxy
Paper i proceeding, 2017

III-nitride-based vertical-cavity surface-emitting lasers have so far used intracavity contacting schemes since electrically conductive distributed Bragg reflectors (DBRs) have been difficult to achieve. A promising material combination for conductive DBRs is ZnO/GaN due to the small conduction band offset and ease of n-type doping. In addition, this combination offers a small lattice mismatch and high refractive index contrast, which could yield a mirror with a broad stopband and a high peak reflectivity using less than 20 DBR-pairs. A crack-free ZnO/GaN DBR was grown by hybrid plasma-assisted molecular beam epitaxy. The ZnO layers were approximately 20 nm thick and had an electron concentration of 1×1019 cm-3, while the GaN layers were 80-110 nm thick with an electron concentration of 1.8×1018 cm-3. In order to measure the resistance, mesa structures were formed by dry etching through the top 3 DBR-pairs and depositing non-annealed Al contacts on the GaN-layers at the top and next to the mesas. The measured specific series resistance was dominated by the lateral and contact contributions and gave an upper limit of ~10-3Ωcm2 for the vertical resistance. Simulations show that the ZnO electron concentration and the cancellation of piezoelectric and spontaneous polarization in strained ZnO have a large impact on the vertical resistance and that it could be orders of magnitudes lower than what was measured. This is the first report on electrically conductive ZnO/GaN DBRs and the upper limit of the resistance reported here is close to the lowest values reported for III-nitride-based DBRs.

hybrid PAMBE

GaN

DBR

electrical conductivity

VCSEL

ZnO

Författare

Filip Hjort

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

Seyed Ehsan Hashemi

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

David Adolph

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

Tommy Ive

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

Åsa Haglund

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

Proceedings of SPIE - The International Society for Optical Engineering

0277786X (ISSN) 1996756X (eISSN)

Vol. 10104 1010413-1 1010413

Styrkeområden

Nanovetenskap och nanoteknik

Materialvetenskap

Ämneskategorier

Telekommunikation

Nanoteknik

Annan elektroteknik och elektronik

Infrastruktur

Nanotekniklaboratoriet

DOI

10.1117/12.2250126

ISBN

978-1-5106-0649-4