Buried graphene electrodes on GaN-based ultra-violet light-emitting diodes

Abstract

We report that the oxidation of graphene-based highly transparent conductive layers to AlGaN/GaN/AlGaN ultra-violet (UV) light-emitting diodes (LEDs) was suppressed by the use of SiNX passivation layers. Although graphene is considered to be an ideal candidate as the transparent conductive layer to UV-LEDs, oxidation of these layers at high operating temperatures has been an issue. The oxidation is initiated at the un-saturated carbon atoms at the edges of the graphene and reduces the UV light intensity and degrades the current-voltage (I-V) characteristics. The oxidation also can occur at defects, including vacancies. However, GaN-based UV-LEDs deposited with SiNX by plasma-enhanced chemical vapor deposition showed minimal degradation of light output intensity and I-V characteristics because the graphene-based UV transparent conductive layers were shielded from the oxygen molecules. This is a simple and effective approach for maintaining the advantages of graphene conducting layers as electrodes on UV-LEDs.

Enhanced performance of photonic crystal GaN light-emitting diodes with graphene transparent electrodes

“…However, it is not appropriate for ultraviolet (UV) GaN LED [12,13]. In addition, the price of the ITO has been increasing for scarce of indium [14][15][16][17]. What's more, ITO is unstable in chemical solutions [12,15,16].…”

“…The 2D intensity is over twice higher than that of G intensity. The lower D peak reveals the good quality of the graphene [17]. Figure 3 exhibits the transmission spectra of the graphene conducting electrodes.…”

“…What's more, ITO is unstable in chemical solutions [12,15,16]. Graphene, a 2D monolayer of carbon atoms, has recently attracted tremendous attention for its excellent optical, mechanical, and electrical properties, such as high transparency in the UV region, ultra-fast mobility, high thermal conductivity, and high mechanical strength [12][13][14][15][16][17][18]. It may be used as an alternative to the ITO in LED.…”

Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures

“…Kim et al. [21] demonstrated GaN-based light-emitting diodes where the conductivity of graphene was substantially improved when capped with silicon nitride (SiNx) but did not discuss the electrostatic impact of the fixed charges trapped in the SiNx. Gluba et al [24] studied CVD graphene capped with a-Si:H and polycrystalline silicon.…”

“…In that regard, a lot of work has been devoted to the study of more or less stable organic or inorganic materials deposited onto graphene [11][12][13], [14], [15], [16]. Field effect doping and dopant incorporation at these interfaces allow the modulation of the work function, the carrier density and sheet resistance as well as the mobility [17][18][19][20][21], [22], [23]. Kim et al.…”