Lasing Characteristics and Reliability of 1550 nm Laser Diodes Monolithically Grown on Silicon

Abstract

Room‐temperature continuous wave (RT‐CW) electrically pumped 1550 nm indium phosphide (InP)‐based laser diodes are realized on complementary metal‐oxide‐semiconductor (CMOS) compatible silicon (Si) substrates by direct heteroepitaxy. Dynamic properties are investigated by gain switching and small signal modulation measurements. A maximum 3 dB bandwidth of 5.3 GHz is demonstrated, along with a narrow optical pulse with a width of 1.5 ns. The dark current density of 490 mA cm−2 at −1 V bias is an order of magnitude higher than identical devices grown and fabricated on native InP substrates. Also, reliability measurements and failure analysis are carried out for the lasers on Si. The lasers operate stably over 200 hours (h) at 10 °C under CW operation without apparent change in threshold or output power. In sharp contrast, a rapid failure occurs at 60 °C under pulsed operation following 5.6 h of aging. To further improve device characteristics for lasers on Si, the dislocation density of the InP template is reduced by introducing a 2 μm‐thick compositionally graded In0.4Ga0.6 As buffer. The resulting surface defect density is as low as 4.5 × 107 cm−2, which is expected to improve the performance and reliability of long wavelength lasers grown directly on Si.