Fabrication and characterisation of InGaAs Gunn diode-based light emitting device

In this study, light emission mechanism and Gunn oscillations of n-type InGaAs-based Gunn devices emitting at a wavelength of 1605 nm based on the Gunn effect were investigated. A 5µm thick InxGa1-xAs (x=0.53) epilayer was grown on lattice-matched semi-insulating InP using Metal Organic Vapor Phase Epitaxy (MOVPE). Structural characterizations were made by Scanning Electron Microscope (SEM) and Energy Dispersive X- Ray Spectroscopy (EDS) InxGa1-xAs-based Gunn devices have been fabricated in different geometries with a various channel lengths by photolithography and electron beam lithography methods. The emission wavelength of the diode was determined from the analyses of the photoluminescence measurements. Hall effect was utilised to find electron density and electron mobility. High-speed current-voltage measurement was conducted to determine the Negative Differential Resistance (NDR) region and to observe Gunn oscillations. Electroluminescence (EL) was ussed to measure the emission spectrum, and the integrated EL versus electric field were carried out to determine threshold electric field of the light emission. The device defined in simple bar with stepped anode region exhibits NDR characteristic and stable Gunn oscillations. The frequency of stable Gunn oscillations originated from intervalley transfer of hot electrons is determined as 1 GHz when NDR condition is satisfied. Light emission originating from the band-to-band recombination of excess carriers generated by impact ionization in Gunn domain is observed at electric fields around the NDR threshold. And its intensity drastically increases above NDR thereshold regardless of voltage polarity. The intensity of the spectral EL peak observed at 1605 nm increases with the applied electric field above NDR threshold electric field.