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.