Design and Layout of Multi GHz Operation of Light Emitting Diodes
Keywords: LET, LED, modulation, GHz, spontaneous
A new high-speed form of light emitting diode (LED) is demonstrated by utilizing an n-type buried “drain” layer beneath the p-type “base” quantum-well (carrier and photon) active region. The asymmetric two-junction LED employs the “drain” layer to tilt and pin the charge in the manner of a heterojunction bipolar light emitting transistor (HBLET), thus preserving the fast recombination lifetime in the order of carrier transit time in the thin base design (_B ~ _ t) by removal of excess slow-recombining carriers in the base. A modified layout based on the tilted-charge LED characteristics is designed to further reduce the parasitics compared to conventional aperture design, and significantly enhance the spontaneous optical modulation bandwidth toward multi-GHz operation.