Electrical Behavior of Vertical Pt/Au Schottky Diodes on GaN Homoepitaxy

Abstract

Schottky barrier diodes on GaN on GaN substrates are fabricated for the purpose of material and technology characterization. The epitaxial layers are grown by MOCVD. I–V measurements as a function of the temperature in the range 80–480 K show ideality factor (n) and barrier height (ϕB) variations not following a thermionic (TE) model. Consequently, barrier height fluctuations are considered. In the temperature range 280–480 K, an average barrier height of 1.31 eV with a relatively large standard deviation (σ) of 0.15 eV is extracted using this model. The n(T) variation is also analyzed in order to extract the field sensibility of 1) the mean barrier height variation (ρ2 = −0.1) and 2) the barrier height standard deviation (ρ3 = −15 mV). The corrected Richardson plot using ϕB and σ values is linear and gives a Richardson constant of 31.5 A cm−2 K−2 close to the theoretical value of 26.4 A cm−2 K−2. For a deeper understanding of ϕB fluctuation origins, micro‐Raman mapping of the epitaxial layers and deep‐level transient spectroscopy (DLTS) are used. μ‐RS mappings show compressive strain for diodes having suffered electrical breakdown. DLTS analysis shows the presence of nine levels whose signatures are extracted and nature discussed.