Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes

Polarized photoluminescence (PL) spectra from nonpolar m-plane InGaN multiple quantum wells (MQWs) in blue laser diode wafers fabricated on m-plane GaN substrates were measured as a function of temperature. The polarization ratio (ρ) and the energy difference between the highest and the second highest valence bands estimated from the energy difference between PL peaks (ΔE) increased with increasing InN molar fraction x (or the estimated anisotropic compressive strain along the m-axis εyy) in the MQWs. The values of ρ at 300K and ΔE were 0.71 and 76meV for the case of 430nm PL peak (x=0.104, εyy=+0.75%) and 0.92 and 123meV for the case of 485nm PL peak (x=0.175, εyy=+1.26%). These results suggest that the preferred stripe direction is the c axis for nonpolar m-plane laser diodes in the region from violet to near green.