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Electrically conductive ZnO/GaN distributed Bragg reflectors grown by hybrid plasma-assisted molecular beam epitaxy

Filip Hjort (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Seyed Ehsan Hashemi (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; David Adolph (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Tommy Ive (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Åsa Haglund (Institutionen för mikroteknologi och nanovetenskap, Fotonik)
Proceedings of SPIE - Gallium Nitride Materials and Devices XII / Photonics West, Jen-Inn Chyi; Hiroshi Fujioka; Hadis Morkoç; Yasushi Nanishi; Ulrich T. Schwarz; Jong-In Shim, San Francisco, 30 January-2 February, 2017 Vol. 10104 (2017), p. 1010413-1010413-9.
[Konferensbidrag, refereegranskat]

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.

Nyckelord: ZnO, GaN, hybrid PAMBE, DBR, electrical conductivity, VCSEL


Copyright 2017 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.



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Denna post skapades 2017-03-06. Senast ändrad 2017-05-12.
CPL Pubid: 248439

 

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