RESUMO
Aluminum nitride (AlN) films have been grown using novel technological approaches based on plasma-enhanced atomic layer deposition (PEALD) and in situ atomic layer annealing (ALA). The growth of AlN layers was carried out on Si<100> and Si<111> substrates at low growth temperature. The investigation of crystalline quality of samples demonstrated that PEALD grown layers were polycrystalline, but ALA treatment improved their crystallinity. A thick polycrystalline AlN layer was successfully regrown by metal-organic chemical vapor deposition (MOCVD) on an AlN PEALD template. It opens up the new possibilities for the formation of nucleation layers with improved quality for subsequent growth of semiconductor nitride compounds.
RESUMO
Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses that arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT) emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN) based DDCT devices, and an outlook of potential DDCT has for opto- and microelectronics.