High conductive gate leakage current channels induced by In segregation around screw- and mixed-type threading dislocations in lattice-matched InxAl1−xN/GaN heterostructures

Abstract

A correlation between microstructures and high gate leakage current density of Schottky contacts on lattice-matched InxAl1−xN/GaN heterostructures has been investigated by means of current-voltage measurements, conductive atom force microscopy (C-AFM), and transmission electron microscopy (TEM) investigations. It is shown that the reverse-bias gate leakage current density of Ni/Au Schottky contacts on InxAl1−xN/GaN heterostructures is more than two orders of magnitude larger than that on AlxGa1−xN/GaN ones. C-AFM and TEM observations indicate that screw- and mixed-type threading dislocations (S/M-TDs) are efficient leakage current channels in InxAl1−xN barrier and In segregation is formed around S/M-TDs. It is believed that In segregation around S/M-TDs reduces local Schottky barrier height to form conductive channels and leads to high leakage current density of Schottky contacts on InxAl1−xN/GaN heterostructures.

Deep traps in GaN-based structures as affecting the performance of GaN devices

“…Their DLTS peaks amplitude demonstrates the logarithmic dependence on the injection pulse length expected for correlated charge capture by defects on dislocation line [11]. At the same time, particularly when analysing the leakage current attributable to dislocations in HEMTs and LEDs, one observes strong indications of the presence of Ga, Al or In-core filled dislocations in GaN, InGaN, AlGaN, and InAlN [60][61][62]. The main effects here are the excessive leakage via the metal-like dislocation core and the local changes of the barrier height in Schottky diodes and p-n junctions as caused by the existence of such channels.…”

Intrinsic degradation mechanism of nearly lattice-matched InAlN layers grown on GaN substrates

“…29,30 When growth is done on a GaN template grown on a foreign substrate, threading dislocations are indeed present in the GaN template with a high density be at the origin of V-defects for InGaN 34 or InAlN layers. [20][21][22][23] Other possibilities for the nucleationof V-defects have been proposed. Dopants were shown to increase the V-defect density in GaN 50 and InAlN layers.…”

“…V-defects (or V-pits) are inverted empty pyramids with a hexagonal base, and they aregenerally attributed to threading dislocations. [20][21][22][23] In addition to the abovementioned structural defects, InAlN layers were shown to degrade with increasing thickness. 24 Thus homogeneous layers with a given composition give birth to an upper layer with a higher or a lower indium composition.…”

“…V-defects appearance for 100 nm thick layers observation was done for all the V-defects we observed.This is consistent with the fact that the density of V-defects observed by AFM on this layer is two orders of magnitude larger than the nominal density of threading dislocations.Bothfor InGaN 34 and InAlN layers, [20][21][22][23] V-defects are generally attributed to threading dislocations. However, some authors have also mentioned the presence of V-defects not associated to any threading dislocations in InAlN layers.…”

Defect investigation in Al0.87In0.13N/AlN/GaN heterostructures by scanning force microscopy methods

“…Channels are a series of V-pits situated in proximity and as a result appear continuous. It is known that indium preferentially segregates at the core of threading dislocations on the GaN surface [1,13,14]. As the AlInN layer grows, threading dislocations propagate towards the surface forming an In-rich or metallic indium nano-pipe extending from the AlInN/GaN interface to the AlInN surface.…”