Room-temperature direct bandgap electroluminesence from Ge-on-Si light-emitting diodes

Abstract

We report the first demonstration of direct band gap electroluminescence (EL) from Ge/Si heterojunction light emission diodes (LEDs) at room temperature. In-plane biaxial tensile strain is used to engineer the band structure of Ge to enhance the direct gap luminescence efficiency by increasing the injected electron population in the direct Γ valley. Room temperature EL is observed at the direct gap energy from a Ge/Si p-i-n diode exhibiting the same characteristics of the direct gap photoluminescence (PL) of Ge. The integral direct gap EL intensity increases superlinearly with electrical current due to an indirect valley filling effect. These results indicate a promising future of tensile strained Ge-on-Si for electrically pumped, monolithically integrated light emitters on Si.

Ge-on-Si photonic devices for photonic-electronic integration on a Si platform

“…11(a), photoluminescence (PL) measurements under a high excitation (4 mW of 457-nm laser light with ∼2 µm in diameter) showed a light emission around 1.55 µm from Ge layers on Si as well as from bulk Ge. Electroluminescence (EL) can be also obtained for vertical Ge pn diodes on Si under forward biases [40,41,42] and for lateral pn diodes of Ge fabricated with standard CMOS processes [43,44]. Fig.…”

Strong Electro-Absorption in GeSi Epitaxy on Silicon-on-Insulator (SOI)

“…Not only have Ge-on-Si based photodectors been extensively investigated in recent years, new applications, such as Ge light emitters [24] and Ge lasers [25] were also successfully demonstrated on the Si platform. Prior to these works, more than thirty years of effort has been devoted to the material science of GeSi in search for a direct gap, emissive device.…”

Extended Defect Propagation in Highly Tensile-Strained Ge Waveguides

“…Many approaches to inducing tensile strain for Ge lasers and more efficient light emitters have been demonstrated [11][12][13][14][15][16][17][18][19]. The first optically pumped Ge laser used 0.15% biaxial strain plus degenerate n-type doping to partly populate the Γ valley with electrons despite the indirect bandgap [2].…”