In-situ reflectance monitoring during MOCVD of AlGaN

Abstract

We report in-situ optical reflectance monitoring during the metalorganic chemical vapor deposition (MOCVD) growth of (Al)GaN. In addition to the well-known thin film interference effect which enables a real-time determination of growth rate, we show that several insights about the MOCVD growth process can be gained by using this simple yet powerful technique. Illustrations from a variety of applications for in-situ reflectance monitoring, specifically the study of growth evolution, the control of alloy fractions, and the use of growth rate to gauge surface kinetics and gas injection will be reported.

Heteroepitaxy of AlGaN on bulk AlN substrates for deep ultraviolet light emitting diodes

“…The deterioration of morphology at this stage is correlated with decay in in situ optical reflectance signal, suggesting that surface roughening on a scale of optical wavelength has occurred. 13 Previous studies 5,14,15 of AlGaN growth on sapphire or Si ͑111͒ substrates have shown that the compressive strain is effectively relaxed through the inclination of preexisting dislocations ͑5 ϫ 10 9 -3ϫ 10 10 cm −2 ͒; good agreement was obtained based on an analytical model ͑ av = bh tan͑͒ / 4, with av the average relaxation, b the Burgers vector, h the film thickness, the dislocation density, and the dislocation inclination angle͒.…”

Monitoring and Controlling of Strain During MOCVD of AlGaN for UV Optoelectronics

“…We also simultaneously obtain information on the surface roughness and film thickness during deposition by monitoring the intensity of one of the reflected laser beams, similar to the method described in Ref. [19]. Figure 3 shows the stress-thickness product (σ f h f ) and the reflected beam intensity as functions of growth time (see the following explanation) during growth of an AlGaN (Al~15%) layer on a 0.6 µm GaN layer grown at 1050°C.…”

“…Figure 3 shows the stress-thickness product (σ f h f ) and the reflected beam intensity as functions of growth time (see the following explanation) during growth of an AlGaN (Al~15%) layer on a 0.6 µm GaN layer grown at 1050°C. We have reported that [19] in-situ reflectance could provide the information of growth rate from the periodicity of Fabry-Perot interference. Such information in turn enables the conversion of time axis into film thickness (h f ).…”

The Behavior of Ion-Implanted Hydrogen in Gallium Nitride

“…The MOCVD GaN films were grown with (0001) orientation and thicknesses in the range 1.4-2.3 µm as discussed elsewhere [6]. The nominally undoped material was of n-type with a free-carrier density of ~10 17 cm -3 as determined by conductivity and Hall-effect measurements.…”