GaN-based blue/green semiconductor laser

High-power InGaN single-quantum-well (SQW) structure blue/green light-emitting diodes (LEDs) with an output power of 3-5 mW were fabricated. The continuous-wave operation of bluish-purple InGaN multiquantum-well (MQW)-structure laser diodes (LDs) was achieved at room temperature with a lifetime of 35 h. The threshold current and the voltage of the LD were 80 mA and 5.5 V, respectively. Photocurrent spectra of the InGaN SQW LEDs and MQW LDs were measured at room temperature. The Stokes shifts of the energy difference between the absorption and the emission energy of the blue/green InGaN SQW LED´s and MQW LDs were 290, 570, and 190 meV. Both spontaneous and stimulated emission of the LDs originated from this deep localized energy state which is equivalent to a quantum dot-like state. When the temperature or the operating current of the LDs was varied, large mode hopping of the emission wavelength was observed. The carrier lifetime and the threshold carrier density were estimated to be 4.7 ns and 1×10²⁰/cm³, respectively. The optical confinement factor (Γ) of the InGaN MQW LDs was estimated to be 0.025 from the measurement of the near-field radiation patterns