  Silicon-based light sources including light-emitting diodes (LEDs) and laser
diodes (LDs) for information transmission are urgently needed for developing
monolithic integrated silicon photonics. Silicon doped by ion implantation with
erbium ions (Er$^{3+}$) is considered a promising approach, but suffers from an
extremely low quantum efficiency. Here we report an electrically pumped
superlinear emission at 1.54 $\mu$m from Er/O-doped silicon planar LEDs, which
are produced by applying a new deep cooling process. Stimulated emission at
room temperature is realized with a low threshold current of ~6 mA (~0.8
A/cm2). Time-resolved photoluminescence and photocurrent results disclose the
complex carrier transfer dynamics from the silicon to Er3+ by relaxing
electrons from the indirect conduction band of the silicon. This picture
differs from the frequently-assumed energy transfer by electron-hole pair
recombination of the silicon host. Moreover, the amplified emission from the
LEDs is likely due to a quasi-continuous Er/O-related donor band created by the
deep cooling technique. This work paves a way for fabricating superluminescent
diodes or efficient LDs at communication wavelengths based on rare-earth doped
silicon.
