Abstract
Monolithic integration of III–V semiconductor lasers with Si circuits can reduce cost and enhance performance for optical interconnects dramatically. We propose and investigate plasmonic III–V nanolasers as monolithically integrated light source on Si chips due to many advantages. First, these III–V plasmonic light sources can be directly grown on Si substrates free of crystallographic defects due to the submicron cavity footprint (250 nm × 250 nm) being smaller than the average defect free region size of the heteroepitaxial III–V material on Si. Secondly, the small lateral and vertical dimensions facilitate process co-integration with Si complementary metal-oxide-semiconductor (CMOS) in the front end of the line. Thirdly, combining with monolithically integrated CMOS circuits with low device capacitance and parasitic capacitance, the nano-cavity optoelectronic devices consume orders of magnitude less power than the conventional lasers and reduce the energy consumption. Fourthly, the modulation bandwidth of the plasmonic light-sources is enhanced to significantly higher than conventional lasers due to enhanced photon state density and transition rate. In addition, we show that these device performance are very robust after taking into account the surface recombination and variations in device fabrication processes.
Highlights
An on-chip light source is preferred over being off-chip for optical interconnects for various reasons1,2; 1) the power loss from couplers and splitters is saved for on-chip sources. 2) on-chip laser can be directly modulated, eliminating the need to deploy modulators
In the second monolithic approach, the laser structure is monolithically grown on the Si substrate via a selective growth in a hole patterned on a SiO2 mask layer (Fig. 1b)
The active regions of all these plasmonic nano-cavities consist of GaAs (10 nm)/Al0.3Ga0.7As (10 nm) multiple quantum wells (MQW)
Summary
An on-chip light source is preferred over being off-chip for optical interconnects for various reasons1,2; 1) the power loss from couplers and splitters is saved for on-chip sources. 2) on-chip laser can be directly modulated, eliminating the need to deploy modulators. While III–V lasers monolithically grown on Si were demonstrated decades ago, the prevailing challenge of these devices remains the short laser lifetimes due to a high defect density in the heteroepitaxial material[4,5,6]. Besides the advantage of small cavity size, monolithic integration of nanolasers on Si can dramatically reduce energy consumption of the networking fabric in large-scale computing and data centers. This is because nanometer-scale lasers and photodetectors have a lower capacitance, and feature unique internal physical effects, which allow for a more efficient photon utilization inside the gain material. Growing III–V nano-photonics components on Si monolithically in conjunction with Si and III-V electronics will eventually meet the requirement of 100 s of GHz bandwidth and fJs/bit energy efficiency for the ever growing optical data transmission demands in data centers and high performance computers
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