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 ( Δ E ) increased with increasing InN molar fraction x (or the estimated anisotropic compressive strain along the m -axis ε yy ) in the MQWs. The values of ρ at 300 K and Δ E were 0.71 and 76 meV for the case of 430 nm PL peak ( x = 0.104 , ε yy = + 0.75 % ) and 0.92 and 123 meV for the case of 485 nm PL peak ( x = 0.175 , ε yy = + 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.