Abstract
This work presents a monolithic laterally-coupled wide-spectrum (350 nm < λ < 1270 nm) optical link in a silicon-on-insulator CMOS technology. The link consists of a silicon (Si) light-emitting diode (LED) as the optical source and a Si photodiode (PD) as the detector; both realized by vertical abrupt n+p junctions, separated by a shallow trench isolation composed of silicon dioxide. Medium trench isolation around the devices along with the buried oxide layer provides galvanic isolation. Optical coupling in both avalanche-mode and forward-mode operation of the LED are analyzed for various designs and bias conditions. From both DC and pulsed transient measurements, it is further shown that heating in the avalanche-mode LED leads to a slow thermal coupling to the PD with time constants in the ms range. An integrated heat sink in the same technology leads to a ∼ 6 times reduction in the change in PD junction temperature per unit electrical power dissipated in the avalanche-mode LED. The analysis paves way for wide-spectrum optical links integrated in smart power technologies.
Highlights
Integrated optical interconnects cater to high speed transceiver [1] applications, and to smart-power applications where data needs to be transferred between galvanically isolated voltage domains [2, 3]
Operating a Si light-emitting diode (LED) in forward mode (FM) yields infrared (IR) electroluminescence (EL) (λ ∼ 1000-1270 nm) [4,5,6,7]. This emission spectrum has a small overlap with the spectral responsivity of Si photodiodes (PDs) [8] resulting in a low internal quantum efficiency (IQE) of the PD
The dependency of η on IAMLED reflects the efficiency of radiative recombination in the AMLED, which is sensitive to the current level
Summary
Integrated optical interconnects cater to high speed transceiver [1] applications, and to smart-power applications where data needs to be transferred between galvanically isolated voltage domains [2, 3]. Operating a Si light-emitting diode (LED) in forward mode (FM) yields infrared (IR) electroluminescence (EL) (λ ∼ 1000-1270 nm) [4,5,6,7] This emission spectrum has a small overlap with the spectral responsivity of Si photodiodes (PDs) [8] resulting in a low internal quantum efficiency (IQE) of the PD. Operating a Si LED in avalanche mode (AM) yields broad-spectrum EL (λ ∼ 350-900 nm) [10,11,12,13] with a reported IQE of ∼ 10−5 [12] This EL spectrum has a significant overlap with the spectral responsivity of Si (PDs) [8] resulting in a high IQE of the PD.
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