500-nm Optical Gain Anisotropy of Semipolar (11(2)over-bar2) InGaN Quantum Wells

We studied the effect of carrier population on light emission polarization of green InGaN quantum wells (QWs) on the semipolar (11 (2) over bar2) plane. The 3nm thick QWs emitting light at about 540 nm at low pumping power have electrical field (E) component E parallel to [(1) over bar(1) over bar 23] stronger than that E parallel to [1 (1) over bar 00]. However, we found that increasing the pumping power changed the sign of the polarization ratio. Using the varied stripe length (VSL) method, we measured the optical gain for light propagating parallel to [(1) over bar(1) over bar 23] direction to be similar to 2 times that of light propagating parallel to [1 (1) over bar 00] direction. We explain this behavior by inhomogeneous QW state filling. (C) 2009 The Japan Society of Applied Physics.