Charge carrier transport and electroluminescence in atomic layer deposited poly-GaN/c-Si heterojunction diodes

Abstract

In this work, we study the charge carrier transport and electroluminescence (EL) in thin-film polycrystalline (poly-) GaN/c-Si heterojunction diodes realized using a plasma enhanced atomic layer deposition (PE-ALD) process. The fabricated poly-GaN/p-Si diode with a native oxide at the interface showed a rectifying behavior (I on /I off ratio ∼ 10 3 at ±3 V) with current-voltage characteristics reaching an ideality factor n of ∼ 5.17. The areal (J a ) and peripheral (J p ) components of the current density were extracted and their temperature dependencies were studied. The space charge limited current (SCLC) in the presence of traps is identified as the dominant carrier transport mechanism for J a in forward bias. An effective trap density of 4.6x10 17 /cm 3 at a trap energy level of 0.13 eV below the GaN conduction band minimum was estimated by analyzing J a . Other basic electrical properties of the material such as free carrier concentration, density of states in the conduction band, electron mobility and dielectric relaxation time were also determined from the current-voltage analysis in the SCLC regime. Further, infrared EL corresponding to the Si bandgap was observed from the fabricated diodes. The observed EL intensity from the GaN/p-Si heterojunction diode is ∼ 3 orders of magnitude higher as compared to the conventional Si only counterpart. The enhanced infrared light emission is attributed to the improved injector efficiency of the GaN/Si diode because of the wide bandgap of the poly-GaN layer and resulting band discontinuity at the GaN/Si interface.

Thermal Atomic Layer Deposition of Polycrystalline Gallium Nitride

“…At long purge durations, when the gas-phase components are sufficiently depleted, the GPC stabilizes. For instance, for GaN films prepared by plasma-enhanced ALD with NH 3 plasma, 30 the GPC indeed shows the expected behavior ( Figure S4b). However, for thermal GaN ALD explored here, this is clearly not the case.…”

“…26,28,29 The relaxation of the necessity of buffer-layers also enables poly-GaN to be directly grown on the corresponding substrates. 30 Poly-GaN layers can be prepared by a variety of techniques; 19,29 among them, atomic layer deposition (ALD) is highly relevant since the technique has become a major player in the electronics industry, owing to its monolayer-level thickness control combined with excellent spatial uniformity and conformality. 31−35 For poly-GaN ALD (further referred to as GaN ALD), organometallic (e.g., trimethylgallium (TMG) or triethylgallium (TEG)) or halide-based inorganic Ga precursors (e.g., GaCl 3 ) have been used, often utilizing NH 3 or N 2 -H 2 as a nitrogen source.…”

Towards electrostatic doping approaches in ultra-thin body semiconductor materials and devices

“…Generally, polycrystalline semiconductor devices do not perform up to par with their crystalline counterparts. For device applications in polycrystalline material several challenges should be taken into consideration [28,35,42], such as obtaining large grain size and reducing the amount of grain boundaries and their role in charge transport, good device stability and reliability, obtaining low defect densities and improving the carrier mobility and lifetime, and good interface control with metals and dielectrics.…”

“…• Chapter 6: The polycrystalline GaN/p-Si heterojunction diode, based on work published in the Journal of Applied Physics, 2018 [42]. This chapter investigates the charge carrier transport and electroluminescence properties of plasma-enhanced ALD deposited poly-GaN/p-Si diodes.…”

“…(a) Schematic cross-section of the experimental Al/GaN/p-Si diode with circular electrode (area A E ) of diameter d=100 µm, (b) Cross-section TEM image of the fabricated device[42,223].…”