TABLE I. Summary of the structural parameters of the shallow QWs in three samples extracted from the XRD (004) ω/2θ scan measurements and the corresponding performances of LED devices.

Results and Discussion

FIG. 2. (a) Current-voltage characteristics of Sample A, B, and C. (b) Inte-grated EL intensity of Sample A, B, and C as a function of injection current.

turn-on voltage

Sample A 2.70 V

Sample B 2.75 V

Sample C 3.05 V

@ ( 1 mA )

EL intensities

Sample A 1.94

Sample B 1.70

Sample C 1.23

Under 20 mA (40 A/cm2)

14%57%

lighting efficiency (light output/electric power input)

FIG. 3. Reciprocal space mapping around GaN asymmetric (10.5) diffrac-tion of (a) Sample A and (b) Sample C.

ε xx

GaN on sapphire -0.23%

Sample A -1.92%

Sample B -1.94%

Sample C -1.98%

InGaN QWs with In% ＝ 16%