| 1. |
|
|
| 2. |
- Ive, Tommy, 1968, et al.
(författare)
-
Design and Fabrication of AlN/GaN Heterostructures for Intersubband Technology
- 2012
-
Ingår i: Japanese Journal of Applied Physics. - 1347-4065 .- 0021-4922. ; 51:1, s. Article Number: 01AG07 -
-
Tidskriftsartikel (refereegranskat)abstract
- We have used models based on the effective-mass approximation and Schrodinger-Poisson to design AlN/GaN multiple quantum well structures for intersubband transitions between two or three energy levels. The structures were realized by molecular beam epitaxy and the surface morphology and structural quality were investigated. We also investigated GaN waveguides that were fabricated using standard cleanroom techniques. Our work is focused on the various challenges associated to the fabrication of quantum cascade lasers based on group III-nitrides. These challenges are discussed in the light of our results.
|
|
| 3. |
- Sun, Jie, 1977, et al.
(författare)
-
Direct Chemical Vapor Deposition of Large-Area Carbon Thin Films on Gallium Nitride for Transparent Electrodes: A First Attempt
- 2012
-
Ingår i: IEEE Transactions on Semiconductor Manufacturing. - : Institute of Electrical and Electronics Engineers (IEEE). - 0894-6507 .- 1558-2345. ; 25:3, s. 494-501
-
Tidskriftsartikel (refereegranskat)abstract
- Direct formation of large-area carbon thin films on gallium nitride by chemical vapor deposition without metallic catalysts is demonstrated. A high flow of ammonia is used to stabilize the surface of the GaN (0001)/sapphire substrate during the deposition at 950 degrees C. Various characterization methods verify that the synthesized thin films are largely sp(2) bonded, macroscopically uniform, and electrically conducting. The carbon thin films possess optical transparencies comparable to that of exfoliated graphene. This paper offers a viable route toward the use of carbon-based materials for future transparent electrodes in III-nitride optoelectronics, such as GaN-based light emitting diodes and laser diodes.
|
|
| 4. |
- Tingberg, Tobias, 1984, et al.
(författare)
-
Investigation of Si and O Donor Impurities in Unintentionally Doped MBE-Grown GaN on SiC(0001) Substrate
- 2017
-
Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 46:8, s. 4898-4902
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the unintentional n-type background doping in GaN(0001) layers grown on semi-insulating 4H-SiC(0001) substrate by plasma-assisted molecular beam epitaxy under Ga-rich conditions at growth temperatures from 780A degrees C and 900A degrees C. All layers exhibited very smooth surface morphology with monolayer steps as revealed by atomic force microscopy. Hall-effect measurements showed that the sample grown at 900A degrees C had carrier concentration of 9.8 x 10(17) cm(-3) while the sample grown at 780A degrees C had resistivity too high to obtain reliable measurements. Secondary-ion mass spectroscopy revealed O and Si concentrations of 10(17) cm(-3) in the sample grown at 780A degrees C. The trend for the atomic concentrations of O and Si, which are common donor impurities in GaN, was thus contrary to the trend of the carrier concentration. The full-width at half-maximum for x-ray rocking curves obtained across the GaN(0002) and GaN(105) reflections for the sample grown at 900A degrees C was 62 arcsec and 587 arcsec, respectively. The half-width increased with decreasing growth temperature. The atomic concentrations of O and Si are too low to account for the unintentional background doping levels. A possible explanation proposed in early reports for the background doping is N-vacancies.
|
|
| 5. |
- Tingberg, Tobias, 1984, et al.
(författare)
-
Step-flow growth of GaN(0001) on 4H-SiC(0001) by plasma-assisted molecular beam epitaxy
- 2016
-
Ingår i: Physica Status Solidi (A) Applications and Materials Science. - : Wiley. - 1862-6319 .- 1862-6300. ; 213:9, s. 2498-2502
-
Tidskriftsartikel (refereegranskat)abstract
- We report on step-flow growth of GaN(0001) on 4H-SiC(0001) substrates by plasma-assisted molecular beam epitaxy. The GaN layers were deposited directly on the substrate without using a buffer layer. A growth temperature of 900 degrees C and above resulted in an atomically flat surface morphology with locally straight steps indicating step-flow growth. The step height was 0.21 nm corresponding to one-half unit cell. The terrace width was 97 nm and the root-mean-square roughness was 0.06 nm. Samples grown below 900 degrees C exhibited a surface morphology consisting of spiraling terraces forming hexagonal hillocks. The full-width at half-maximum for X-ray rocking-curves recorded across the (0002) and (10 (1) over bar5) reflections was as narrow as 62 and 587 arcsec, respectively. We show that the high growth temperature in conjunction with Ga adlayers on the growth front provides a path for achieving step-flow growth of GaN by MBE.
|
|
