Experimental insights toward carrier localization in in-rich InGaAs/InP as candidate for SWIR detection: Microstructural analysis combined with optical investigation

Hyperspectral imaging has been flourished thanks to the huge investigation of the infrared spectrum from NIR to LWIR bands. The ternary InGaAs has been investigated herein in the context of studying the structural dependences of localization phenomenon by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), Raman, ultraviolet–visible (UV–vis), and photoluminescence (PL) techniques. Using metal-organic vapor phase epitaxy (MOVPE), we succeed to grow the InGaAs directly on InP substrate at 560 °C as an active layer with indium concentration exceeding the “golden” value (53%) to enlarge its cutoff absorption wavelength. X-ray diffraction proved a good crystallinity of the heterostructure with a sharp peak related to the thick substrate and another peak attributed to the thin layer of InGaAs. Moreover, an interfacial layer appeared at the logarithmic scale of XRD patterns and was confirmed by Raman analysis. The SEM-EDX revealed an average indium concentration (62%), almost the growth concentration. However, a cross-section compositional profile over the heterostructure showed an inhomogeneous distribution of the indium. This is predictable from the composition fluctuation in the indium-containing alloys and the volatility (surface segregation) of As (In). On the other side, the optical investigation of InGaAs demonstrated an anomalous behavior of luminescence versus temperature, manifested by the S-shape feature. This trend stems from the potential fluctuation induced by the non-uniform distribution of indium. A numerical simulation was developed based on the localized state ensemble (LSE) model to well-reproduce this anomaly by giving the best fitting parameters and comparing them with those calculated using the semi-empirical models (Viña and Pässler). The results reported here will help in optimizing the epitaxy design of future InGaAs/InP and further studying its surface morphology and device performance.