Enhanced Performance Designs of Group-IV Light Emitting Diodes for Mid IR Photonic Applications

Abstract

This paper describes Ge1-y Sn y (y = 0.0-0.11) light emitting diodes (LEDs) with a broad range of compositions extending from pure Ge to Sn concentrations where the alloy becomes a direct gap material (y = 0.09) and beyond. The devices are grown on Si(100) platforms using ultra-low temperature depositions of highly reactive Ge and Sn hydrides. The device fabrication adopts two new photodiode designs. The first employs n-Ge/i-Ge1-y Sn y /p-Ge1-y ’ Sn y ’ hetero-structure stacks possessing a single defected interface between the n-Ge and i-Ge1-y Sn y layers. The second consists of a homo-structure n-Ge1-y Sn y /i-Ge1-y Sn y /p-Ge1- y Sn y design. The devices show low dark currents and the electroluminescence (EL) spectra show concomitant redshifts of the peak emission position and intensity increase near direct gap Sn compositions. The EL of the homo-structure design displays a large efficiency enhancement relative to the hetero-structure devices. The fabrication of ternary Ge1-x-y Si x Sn y diodes with ~9% Sn and 3-9% Si contents is also discussed.