Abstract
Continuous-wave (CW) operation of nonpolar m-plane InGaN/GaN laser diodes (LDs) with the lasing wavelengths approximately 400 nm was demonstrated. The threshold current was 36 mA (4.0 kA/cm2) for the CW operation [28 mA (3.1 kA/cm2) for pulsed mode], being comparable to that of conventional c-plane violet LDs. Both the LDs with the stripes parallel to a- and c-axes showed TE mode operation, according to the polarization selection rules of the transitions in strained InGaN. The c-axis stripe LDs exhibited lower threshold current density, since the lowest energy transition is allowed. As is the case with the m-plane light emitting diodes fabricated on the free-standing m-plane GaN bulk crystals [Okamoto et al.: Jpn. J. Appl. Phys. 45 (2006) L1197], the LDs shown in this paper did not have distinct dislocations, stacking faults, or macroscopic cracks. Nonpolar m-plane GaN-based materials are coming into general use.