Electric fields in AlGaN/GaN quantum well structures

Abstract

This paper presents a comparative study of the magnitude of the electric fields in AlGaN/GaN quantum well structures, measured using electron holography in a transmission electron microscope and estimated from a comparison of low temperature photoluminescence peak energies with calculated values. The values derived from the two techniques were found to be in reasonable agreement for the structures examined here. A larger field across the GaN well was observed from a single quantum well compared to a 10 period structure with equivalent well thickness, while the presence of an electric field across the barrier of the single quantum well was also detected by electron holography.

Solid-State Lighting Based on Light Emitting Diode Technology

“…The impact of the internal field, especially the piezoelectric field caused by strain, on quantum well recombination behaviour has been confirmed experimentally and reported in various III-nitride-based heterostructures [27][28][29][30][31][32]. Redshifts of emission energy and lower emission intensity were found in strained quantum wells based on III-nitrides, confirming the strong influence of the strain-induced piezoelectric field.…”

Precise determination of polarization fields in c-plane GaN/Al x Ga1-x N/GaN heterostructures with capacitance–voltage-measurements

“…photoluminescence and electron holography suffer from uncertainties due to screening effects of additionally generated free carriers. [37][38][39][40] Measuring the density of the 2DEG by Hall-measurements 2) or capacitance-voltage profiling 41) at the AlGaN/GaN interface can suffer from compensating surface states. 2) In addition, various techniques rely on Schrödinger-Poisson simulations to determine the magnitude of the internal polarization field, and thus suffer from uncertainties in the input parameters.…”

X-ray diffraction of III-nitrides

“…However, the reflectivity data are less sensitive to variations in R [94] and will drop off quickly if the sample is too rough, so higher-angle ω-2θ scans are better if the intensities are sufficient to allow multiple highorder SL peaks to be detected. Once R is found reliably, x, t w and t b can be found by fitting simulated data to a second (more detailed) ω-2θ scan of the central region, as demonstrated for InGaN [94] and AlGaN [199].…”

“…In general most QW structures are fully strained [94,199] and suitable elastic constants are required to remove the effects of strain from the measured d h k l and thus to obtain the mean composition of the entire QW stack, followed by the required alloy composition (see section 3.6). However, if biaxial strain is not present [192] x will be incorrect (as for alloy films).…”