Device Design Considerations for a Monolithically Integrated III-Nitride Infrared-Visible Detector-Emitter

Quantum well infrared photodetectors (QWIPs) have been used for applications such as telecommunication and thermal imaging in astronomy and defense. Recently, III-nitride materials have attracted much attention in the design of QWIPs owing to their large conduction band offset (CBO) up to 2 eV [1], which makes it suitable for a variety of intersubband transition (ISBT) energies [2]. The system’s polarization in the c-direction offers additional design flexibility, permitting further tuning of band offset and therefore of ISBT energies.<br/><br/>One of the challenges impeding the use of III-nitride QWIPs in many applications, such as thermal imaging, is the need for wavelength up-conversion to permit emission in the visible range. Without integrated up-conversion, the QWIP must have an additional readout circuit, which increases the device complexity, size, and weight which is undesirable in many applications such as handheld devices. This challenge was overcome in another material system where monolithic integration of a GaAs/AlGaAs QWIP and light emitting diode (LED) was proposed in 1997 [3] and successfully demonstrated [4]. The principle of integrated QWIP-LED for wavelength upconversion is the photoexcitation of carriers from IR spectral radiation in quantum wells by ISBT and then injection of excited carrier towards the LED for generation of visible light [5]. Such structures require precise control over the thickness of layers and interfaces. Growth of several nm thick layers with high quality interfaces (e.g., in QWIP) is quite challenging in metal organic chemical vapor deposition (MOCVD) of III-nitrides. Of key importance in interface quality is the RMS roughness of each layer, controlled by the time lapse between growth of barrier/well/barrier and growth rate in the layers. Thicknesses of less than 5 nm were required in our QWIP design.<br/><br/>In this work, we present for the first time a design for a monolithically integrated III-N detector-emitter with a target absorption wavelength of 1.5 µm and emission in the visible range. Parametric tuning of QWIP layers compositions and thicknesses is performed with parallel simulations using classical (Sentaurus TCAD) and quantum mechanical (nextnano) modelling. The impact of doping and polarization charges at heterointerfaces of the QWIP structure on the band alignment and absorption are discussed. It is found that p-type doping of the QWIP superlattice is required for absorption of TE polarized light. Doping and composition of the transition layers between QWIP and LED were optimized to promote higher carrier injection efficiency. Experimental limitations and experimental material characteristics are considered to achieve a realistic design. We will present characterization of initial proof-of-concept structures grown by MOCVD, comparing simulated design to experimental characteristics.<br/><br/>[1] A. N. Westmeyer et al., J Appl Phys, vol. 99, no. 1, p. 013705, 2006<br/>[2] S. D. Gunapala et al., “IEEE Journal of Selected Topics in Quantum Electronics, vol. 20, no. 6, pp. 154–165, 2014<br/>[3] L. B. Allard, et al., Appl Phys Lett, vol. 70, no. 21, pp. 2784–2786, 1997<br/>[4] E. Dupont et al., Semicond Sci Technol, vol. 23, no. 5, p. 055006, 2008<br/>[5] T. Rao, et al., Coatings, vol. 12, no. 4, p. 456, Mar. 2022