Abstract
As a result of its indirect bandgap, emitting photons from silicon in an efficient way remains challenging. Silicon light emitters that can be integrated seamlessly on a CMOS platform have been demonstrated; however, none satisfies an ensemble of key requirements such as a small footprint, room-temperature operation at low voltages, and emission of narrow and polarized lines with a high spectral power density in the near-infrared range. Here, we present an all-silicon electrically driven light emitting diode that consists of an inversely tapered half-ellipsoidal silicon photonic resonator containing a p–n junction used to excite whispering gallery modes (WGMs) inside the resonator. Under low voltage operation at room temperature, such a photonic silicon light-emitting diode exhibits a band-edge emission (900–1300 nm) with a wall-plug efficiency of 10−4. The emitted spectrum is amplified in multiple WGMs and shows peaks that are polarized and have linewidths Δλ as narrow as 0.33 nm and spectral power densities as high as 8 mW cm−2 nm−1. Considering its small footprint of ∼1 µm and remarkable emission characteristics, this silicon light source constitutes a significant step ahead toward fully integrated on-chip silicon photonics.
Highlights
Integration of III–V semiconductors by bonding or epitaxial growth has brought remarkable progress toward small footprint and CMOS-compatible on-chip optical emitters
Si-light-emitting diodes (LEDs) fabricated from optically doped photonic crystals could reach small footprints (∼25 μm2) and sharper emission lines (∼1 nm) with a higher spectral output power density; they still suffer from very low wall-plug efficiencies of about 10−8.13 The present study goes one step ahead in small scale Si-LED design
To introduce a p–n junction into the resonators, the reactive ion etching (RIE) process was performed on a wafer with a doping profile designed such that the p–n junction is situated inside the photonic resonator, at a distance from the top of about 750 nm [see Figs. 1(a) and 1(b)], whereas the top and substrate of the structure are degenerately doped (n++ and p++, respectively) to serve as contacts for the electrical connection of the Si-LEDs [see Fig. 1(a)]
Summary
Integration of III–V semiconductors by bonding or epitaxial growth has brought remarkable progress toward small footprint and CMOS-compatible on-chip optical emitters. By the excitation of photonic modes in silicon optical resonators with high energy electron beams, a spectrally selective amplification of cathodoluminescence (1000–1600 nm) could be reached.19,20 Another recent work could demonstrate an enhanced light emission from silicon by controlling its electronic spin properties in strong magnetic fields.. Another recent work could demonstrate an enhanced light emission from silicon by controlling its electronic spin properties in strong magnetic fields.21 Despite these successes, all presented approaches do not simultaneously meet the requirements for high resolution on-chip sensing devices, efficient integrated optical links, or photonic computing architectures.. Si-LEDs fabricated from optically doped photonic crystals could reach small footprints (∼25 μm2) and sharper emission lines (∼1 nm) with a higher spectral output power density; they still suffer from very low wall-plug efficiencies of about 10−8.13 The present study goes one step ahead in small scale Si-LED design. The spectral output is characterized by sharp (0.33 nm) and polarized emission lines between 900 nm and 1300 nm, a very high output power density and spectral output power density (6 ⋅ 105 μW cm−2 and 8 ⋅ 103 μW cm−2 nm−1, respectively) in combination with a relatively high quantum efficiency (10−5) and wall-plug efficiency (10−4)
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