Characteristics of InGaN-based superluminescent diodes with one-sided oblique cavity facet

We have fabricated InGaN-based superluminescent diodes (SLDs) with one-sided oblique facet. The characteristics of the SLDs and laser diodes with the same cavity length (800 μm) were compared. The typical peak wavelength and the full width at half maximum of the spectrum in superluminescence regime are 445.3 and 7.7 nm for the SLDs with 800 μm cavity length. The characteristics of the SLDs with different cavity length were also demonstrated in a comparative way. It is found that the gain of the InGaN multi-quantum wells in blue spectral range is a linear function of the current density below gain saturation region. The lasing threshold current turns out to be higher for the shorter SLD (S-SLD) (400 μm), but the output light intensity of the longer SLD (800 μm) is higher than that of the S-SLD under the same current density. The gain saturation phenomenon was observed in S-SLD when it was biased at a current density larger than 27.5 kA/cm². The increase of junction temperature was identified as the main reason for gain saturation through spectra analysis.