Green, yellow and bright red (In,Ga,Al)P-GaP diode lasers grown on high-index GaAs substrates
Résumé
Low threshold current density (<400 A/cm2) injection lasing in (AlxGa1–x)0.5In0.5P–GaAs–based diodes down to the green spectral range (<570 nm) is obtained. The epitaxial structures are grown on high–index (611)A and (211)A GaAs substrates by metal–organic vapor phase epitaxy and contain tensile–strained GaP–enriched insertions aimed at preventing escape of the injected nonequilibrium electrons from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15o for (611)A substrates. The lasing at 569 nm is realized at 85 K. In the orange–red laser diode structure low threshold current density (200 A/cm2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrate room temperature lasing at 628 nm at ~2 kA/cm2 and a total power above 3W. The red laser diodes grown on (211)A substrates demonstrate vertically multimode lasing far field pattern indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However the temperature stability of the threshold current and the wavelength stability are significantly higher for (211)A–grown structures in agreement with the conduction band modeling data.