Verification of threading dislocations density estimation methods suitable for efficient structural characterization of AlxGa1−xN/GaN heterostructures grown by MOVPE

Abstract

Selection of a suitable chemical etching method for threading dislocations density estimation is crucial for the structural characterization of epilayers grown by MOVPE and thus further for device fabrication. In this work, threading dislocations density in single layer and AlxGa1−xN/GaN periodical heterostructures has been investigated by means of chemical etching and XRD analysis. For chemical etching, two types of agents have been used: phosphoric acid (220°C/7.5min) and a molten mixture of KOH-NaOH (440°C/2.5min). Estimation of dislocation density has been carried out on the basis of SEM images. It was shown that defect-selective etching in molten alkaline solution is more effective than etching in phosphoric acid and provides more accurate data that are in agreement with data obtained from XRD characterization.

High‐Temperature Annealing of AlGaN

“…Big etch pits indicate screw‐type dislocations, whereas smaller pits are formed at positions of edge‐type and mixed dislocations. [ 18 ] The etch pit density (EPD) decreases with increasing annealing temperature (Figure 6), which suggests a decrease in TDD from an initial value of 6.0 × 10 9 down to 2.6 × 10 9 cm −2 due to annealing at 1705 °C. It is particularly striking that the increase in TDD calculated from XRC‐FWHM for the samples annealed at temperatures above 1650 °C is not confirmed by the EPD.…”

Molten Barium Hydroxide as Defect Selective Drop Etchant for Dislocation Analysis on Aluminum Nitride Layers

“…[12][13][14][15][16] In many investigations, it is, therefore, a standard method for determining dislocation densities in many substrate materials including SiC, GaN, AlN, BN, and AlGaN. [12,[17][18][19][20][21] Molten salts are generally preferred, as the use of hot aqueous solutions leads to low etching rates and low sensitivity. [20] Various investigations on defect selective etching of GaN were performed by the Institute of High-Pressure Physics (Warsaw) in DOI: 10.1002/pssa.202100707…”

“…[12,[17][18][19][20][21] Molten salts are generally preferred, as the use of hot aqueous solutions leads to low etching rates and low sensitivity. [20] Various investigations on defect selective etching of GaN were performed by the Institute of High-Pressure Physics (Warsaw) in DOI: 10.1002/pssa.202100707…”

“…[ 12–16 ] In many investigations, it is, therefore, a standard method for determining dislocation densities in many substrate materials including SiC, GaN, AlN, BN, and AlGaN. [ 12,17–21 ] Molten salts are generally preferred, as the use of hot aqueous solutions leads to low etching rates and low sensitivity. [ 20 ]…”

“…[ 12,17–21 ] Molten salts are generally preferred, as the use of hot aqueous solutions leads to low etching rates and low sensitivity. [ 20 ]…”