Cubic InGaN for red emission: Improved phase stability and emission properties by metal-modulated epitaxy

Abstract

Cubic III-nitrides are a promising alternative to conventional wurtzite-based InGaN systems for visible light emission, particularly in the red spectral region, due to the absence of internal polarization fields. We present a systematic study of cubic InGaN layers grown by plasma-assisted molecular beam epitaxy using two different growth schemes: conventional growth and metal-modulated epitaxy (MME). Three types of structures were investigated, namely, bulk layers, multiple quantum wells (MQWs), and single quantum wells (SQWs). MME-grown samples show improved surface morphology and enhanced phase purity, including a complete suppression of hexagonal inclusions. Photoluminescence (PL) measurements confirm red emission from all samples and reveal multiple emission peaks for the quantum well samples. Based on micro-cathodoluminescence mapping, the main emission peak is most likely attributed to carrier recombination in the QW or bulk regions, while the high-energy peak is associated with localized surface features, such as pits. Temperature-dependent PL measurements show different thermal quenching behavior for the two peaks. Power-dependent measurements confirm that all samples exhibit remarkable emission energy stability over nearly two orders of magnitude variation in excitation power. The spectrally integrated PL intensities recorded at various temperatures demonstrate the robust emission efficiency retaining up to 25% of their low-temperature PL intensity at room temperature. These results demonstrate the potential of MME-grown cubic InGaN for efficient red emission and underline its relevance for future micro-LED applications.