Polarization fields in semipolar (202¯1¯) and (202¯1) InGaN light emitting diodes.

In_xGa_1−xN/GaN multiple quantum well structures (x = 0.13 and 0.18) embedded into p–i–n diodes on (20 2 ¯ 1 ¯ ) and (20 2 ¯ 1) oriented GaN substrates were investigated by electroreflectance, photocurrent, and electroluminescence. Transition energies in absorption and emission experiments were measured as a function of the polarization orientation of light and applied bias voltage. The results were analyzed by a perturbation theoretical model to determine polarization fields. For the (20 2 ¯ 1 ¯ ) sample (x = 0.18), the flatband voltage is found at + 1 V corresponding to a polarization field of − 458 kV / cm. For the (20 2 ¯ 1) sample (x = 0.13), the polarization field is estimated to be ≈ + 330 kV / cm at flatband voltage higher than turn-on voltage of this light emitting diode. [ABSTRACT FROM AUTHOR]