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Fabrication and characterization of In0.25Ga0.75N/GaN multiple quantum wells embedded in nanorods
(2005-10-01)
Hsueh, TH
;
Sheu, JK
;
Huang, HW
;
Chang, YH
;
Ou-Yang, MC
ln(0.25)Ga(0.75)N/GaN multiple quantum wells embedded in nanorods with diameters of 60-100nm were fabricated by inductively coupled plasma reactive ion etching with Cl-2/Ar plasma. The strong optical emission of the nanorods, observed by micro-photoluminescence measurement at 80 K, reveals a large blue shift of about 90meV and an increase in photoluminescence intensity density of more than 17-fold, compared with that of the as-grown wafer under the same excitation power density of 80W/cm(2). These nanostructures have a high potential for application in efficient GaN-based vertical cavity emitters.
Beryllium-implanted P-type GaN with high carrier concentration
(2001-05-01)
Yu, CC
;
Chu, CF
;
Tsai, JY
;
Lin, CF
;
Lan, WH
We report the results of beryllium implantation in Mg-doped GaN to obtain a high hole concentration and lower activation energy for Mg. The metal organic chemical vapor deposition (MOCVD)-grown Mg-doped GaN samples were implanted with Be ions at two different energies of 50 keV and 150 keV and a dose of 10(14) cm(-2). The implemented samples were subsequently annealed at 1100 degreesC for 60 s. The annealed samples showed an increase of hole concentration by three orders of magnitude from the non-implanted value of 5.5 x 10(16) to 8.1 x 10(19) cm(-3) as determined by Hall measurement. The activation energy of Mg dopants for the implanted annealed samples estimated from the temperature dependence of the photoluminescence data is about 170 meV, which is nearly 30% lower than that for the as-grown samples.
Investigation of beryllium implanted P-type GaN
(2001-05-22)
Yu, CC
;
Chu, CF
;
Tsai, JY
;
Wang, SC
;
光電工程學系
We report the preliminary results of beryllium implanted into P-type GaN and the effects on the characteristic of Mg-doped P-GaN. These samples were implanted with Be ions were implanted with two different energies of 50 and 150 keV at two different doses of similar to 10(13) and 10(14) cm(-2) at room temperature. Surface morphology and photoluminescence measurements are presented. (C) 2001 Elsevier Science B.V. All rights reserved.
High etching rate of GaN films by KrF excimer laser
(2001-05-22)
Chu, CF
;
Lee, CK
;
Yu, CC
;
Wang, YK
;
Tasi, JY
A study of laser processing of gallium nitride (GaN) material is reported. A pulsed KrF excimer laser at 248 nm with 20-nsec pulse width and 1 Hz repetition rate is used to etch the GaN film. We establish the material etching parameters under different environmental conditions. By changing the pulsed energy at constant pulse numbers, ablation of GaN surface was observed at threshold laser fluence about 0.3 J cm(-2). Laser etching increase with reducing environment pressure. Al 1.0 J cm (-2) laser fluence, the etching fate is about 35 nm per pulse at atmosphere pressure and increases to 60 nm per pulse at low pressure. The etched depth also increases with increasing laser fluence. The surface morphology of the etched surface was also investigated. (C) 2001 Elsevier Science B.V. All rights reserved.
Comparison of p-side down and p-side up GaN light-emitting diodes fabricated by laser lift-off
(2003-02-15)
Chu, CF
;
Yu, CC
;
Cheng, HC
;
Lin, CF
;
Wang, SC
The performance characteristics of laser lift-off (LLO) freestanding InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) mounted on a Cu substrate with p-side up, and p-side down configurations were determined and compared. The InGaN/GaN MQW LED structures, which were originally fabricated on a sapphire substrate, were transferred to a Cu substrate by the LLO process into two different configurations, namely p-side up and p-side down with the same Ni/Pd/Au p-contact metallizations. Both p-side down and p-side up LLO-LEDs showed a higher current operation capability up to 400 mA than the original LEDs on the sapphire substrate. The p-side down LLO-LEDs showed a nearly eightfold increase in the light output power compared to the p-side up LLO-LEDs. The p-side down LLO-LEDs also showed a more stable wavelength emission spectrum than the p-side up ones.
Thermal annealing effects on the optical gain of InGaN/GaN quantum well structures
(2003-03-01)
Chen, CC
;
Hsueh, TH
;
Ting, YS
;
Chi, GC
;
Chang, CA
In this work, the variation of the optical gain in the InGaN/GaN quantum well after thermal annealing is simulated. The potential profile change of the quantum well resulting from the interdiffusion of Ga and In atoms across the interface of the well and the barrier during the thermal treatments is assumed to follow Fick's law. The results show that the thermal annealing can induce an increase of the optical gain in the InGaN/GaN quantum well. The maximum optical gain can be obtained at a diffusion length of 0.4 nm of In and Ga atoms. However, an excessive annealing may result in decreasing the optical gain. There is a good agreement between the experimental data in literature and the optimized diffusion length studied in this work. (C) 2002 Elsevier Science Ltd. All rights reserved.
Characteristics of stable emission GaN-based resonant-cavity light-emitting diodes
(2004-01-19)
Lin, CF
;
Yao, HH
;
Lu, JW
;
Hsieh, YL
;
Kuo, HC
The resonant-cavity light-emitting diode (RC-LED) structure was grown by MOCVD. The structure of RC-LED consisted of a 3lambda InGaN/GaN MQW LED cavity between the top TiO2/SiO2 DBR (81.7%, reflectance) and the bottom AlN/GaN DBR (90.4%) stack. A stable 410 nm emission peak and a low thermally induced red-shift effect (0.12 nm/kA/cm(2)) were measured by varying the injection current density. The light output power of the full RC-LED device was three times higher than the RC-LED without top TiO2/SiO2 DBR layers under 600 A/cm(2) inject current density. The narrow line width of 7.4 nm, emission peak localization at 410 nm, and three times higher output power were caused by the resonance effect in this vertical cavity structure. (C) 2003 Published by Elsevier B.V.
MOCVD growth of AlN/GaN DBR structures under various ambient conditions
(2004-02-15)
Yao, HH
;
Lin, CF
;
Kuo, HC
;
Wang, SC
;
光電工程學系
The high-reflectivity AlN/GaN distributed Bragg reflector (DBR) structures were realized by metal organic chemical vapor deposition (MOCVD) growth under pure N-2 ambient for AlN epilayer growth. The highest peak reflectivity of about 94.5% with a stopband width of 18 nm at a center wavelength of 442 nm was obtained. For the DBR structure with AIN layer grown under mixture of N-2/H-2 and pure H-2 conditions, the center wavelength was blue-shifted to 418 and 371 nm and the peak reflectivity also showed a reduction to 92% and 79%, respectively. The stopband width also decreases with increasing H-2 contents. The surface roughness and the grain size of the grown DBR structures showed an increase with increasing the H-2 ambient gas ratio. For realization of a high reflectivity and broad bandwidth of AlN/ GaN DBR by using the MOCVD growth method, the pure N-2d ambient gas for growth of AIN layer should be preferable and optimal condition. (C) 2003 Elsevier B.V. All rights reserved.
Study of dry etching for GaN and InGaN-based laser structure using inductively coupled plasma reactive ion etching
(2004-03-25)
Kao, CC
;
Huang, HW
;
Tsai, JY
;
Yu, CC
;
Lin, CF
Dry etching of undoped, n-GaN, p-GaN and InGaN laser structure was investigated by inductively coupled plasmas reactive ion etching (ICP-RIE) using Ni mask. As Cl-2/Ar gas flow rates were fixed at 10/25 sccm, the etched surface roughness has the lowest value of 0.2 nm at constant ICP/bias power = 300/100 W and 5 mTorr chamber pressure for undoped GaN. The highest etching rate of 12,000 Angstrom/min for n-GaN was achieved at 30 mTorr, 300 W ICP, 100 W bias power using low Cl-2 flow rate (Cl-2/Ar = 10/25 sccm) gas mixtures. The surface roughness was dependent of bias power and chamber pressure, and shows a low root mean square (rms) roughness value of about I nm at 50 W of bias power for n-GaN and p-GaN. For etching of InGaN laser structure using high O-2 flow rate (Cl-2/Ar = 50/20 sccm) and low chamber pressure 5 mTorr, a smooth mirror-like facet of InGaN laser diode structure was obtained. Using these etching parameters, mirror-like facets can be obtained which can be used for the fabrication of nitride-based laser diodes. Moreover, at the fixed Cl-2/Ar flow rate of 10/25 sccm, ICP/bias power of 200/100 W and chamber pressure of 30 mTorr, the InGaN-based materials nanorods were fabricated with a density of about 10(8) cm(-2) and dimension of 50-100 nm. (C) 2004 Elsevier B.V. All rights reserved.
Effect of rapid thermal annealing on beryllium implanted p-type GaN
(2004-03-25)
Huang, HW
;
Kao, CC
;
Tsai, JY
;
Yu, CC
;
Chu, CF
We report the results of rapid thermal annealing (RTA) effect on beryllium implanted in situ activated p-type GaN samples and investigate the ramping and isothermal annealing effect of RTA process for these samples. It is found that the optimum RTA condition is at the temperature of 1100 degreesC for 15 s. Furthermore, with equal total isothermal time of 60 s, we compared the multiple step annealing (MSA) at 1100 degreesC for four periods with single step annealing (SSA) for one period at the same annealing temperature of 1100 degreesC, and observed that the ramping effect with MSA could repair Be-related complex defect, and one time, long period isothermal annealing effect with SSA seems to induce much more defect. It seems that the multiple step annealing is more effective and induce less defect than single step annealing for Be-implanted in situ activated p-type GaN samples. (C) 2004 Elsevier B.V. All rights reserved.

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