GaN‐based nanowires: From nanometric‐scale characterization to light emitting diodes

Abstract

We studied and improved gallium nitride (GaN) nanowire (NW) based light emitting diodes (LEDs). PIN nanodiodes with and without InGaN/GaN multiple quantum wells (MQWs) were grown by molecular beam epitaxy (MBE) under N-rich conditions on n-doped Si(111) substrates. Thanks to the coalescence of the p-type region of the NWs grown at low temperature, an autoplanarization process has been performed to obtain LEDs. Ni/Au top contacts have been deposited and patterned in order to bias the devices. A multiple-scale characterization approach has been carried out through the comparison of localized cathodoluminescence (CL) and macroscopic electroluminescence (EL) spectra. It shows that the EL emission of PIN-based LED at room temperature is related to defects in the p-type region of the NWs. In order to enhance the radiative recombinations of NW-based LEDs, we have first added InGaN/GaN MQWs, and secondly an electron blocking layer (EBL) has been inserted between the MQWs and the p-type zone of the NWs. The LED with EBL exhibited an emission band at 420 nm. The blue-shift of this emission band with increasing injected current is attributed to quantum confined Stark effect (QCSE) and evidences the radiative emission of InGaN/GaN MQWs. At 50 mA dc current, this improved NW-based LED emits about 500 times more light than the heterostructure without EBL.

GaN based nanorods for solid state lighting

“…114 Similar work is also reported from Bavencove et al, where they also used the coalesced p-GaN layer as the contact layer for nanorod based LED. 122 Their nanorod The electrically injected LEDs based on regular GaN nanoLED arrays were also demonstrated by Hersee et al fabricated via selective area MOVPE growth. 123 The spaces between the GaN nanoLEDs were filled with spin-on dielectric.…”

Influence of the adatom diffusion on selective growth of GaN nanowire regular arrays

“…The catalyst free molecular beam epitaxy ͑MBE͒ growth of GaN NWs on bare Si͑111͒ was investigated by several groups, [3][4][5][6][7][8][9] and the capability of fabricating III-nitride NW devices using single NWs ͑Refs. 10-12͒ and NW ensembles 13,14 has been proven. However, the processes of nucleation [15][16][17][18][19] and diffusion of adatoms [20][21][22][23] on the NW still represent interesting and lively discussion subjects as not all the aspects have been clarified.…”

Heat flow in InAs/InP heterostructure nanowires

“…(1) and (2). Importantly, in this model there are only two physical degrees of freedom that describe how heat flows through the material:…”

“…Note that both δ and λ are dimensionless quantities, and that δ is derived by solving the linearized forms of Eqs. (1) and (2). δ represents the degree of thermal coupling between the electron and phonon systems: δ 1 represents the decoupled state, while δ 1 the coupled state.…”