研究目的
To demonstrate high-performance long-wavelength InAs/GaSb superlattice infrared photodetectors using an Al-free single heterojunction grown by MOCVD, aiming to reduce dark current and achieve performance comparable to MBE-grown detectors.
研究成果
The PNn design with shallow etching effectively suppressed dark current components, achieving high performance with a dark current density of 2.4×10-5 A/cm2, quantum efficiency of 41.2%, and specific detectivity of 7.3×1011 cm·Hz1/2/W at 77 K, comparable to MBE-grown detectors. This demonstrates the viability of MOCVD for mass production of long-wavelength infrared detectors.
研究不足
The study uses n-type absorbers with minority carriers as holes, which have shorter lifetimes and diffusion lengths than electrons, potentially limiting further performance improvements. No antireflection coating was applied, which might affect quantum efficiency. The growth was on conducting InAs substrates, requiring bonding to semi-insulating silicon for carrier concentration measurements.
1：Experimental Design and Method Selection:
The study employed a PNn heterojunction design with a mid-wavelength SL p-n junction and a long-wavelength SL n-type absorber to suppress dark current components. A shallow etch technique was used for pixel isolation to reduce surface leakage.
2：Sample Selection and Data Sources:
The device structure was grown on (001) InAs substrates using MOCVD. Samples included test structures for material characterization and fabricated detectors for performance evaluation.
3：List of Experimental Equipment and Materials:
Equipment included MOCVD system for growth, inductively coupled plasma (ICP) dry etching for fabrication, plasma enhanced chemical vapor deposition (PECVD) for passivation, reactive ion etch (RIE) for apertures, and Nicolet IS50 FTIR system for spectral response measurement. Materials included InAs substrates, Si and Zn dopants, Ti/Pt/Au for contacts, and SiO2 for passivation.
4：Experimental Procedures and Operational Workflow:
The PNn structure was grown, characterized using photoluminescence (PL) and X-ray diffraction (XRD), fabricated with shallow and deep etching, passivated, and electrically and optically tested at 77 K.
5：Data Analysis Methods:
Dark current density, responsivity, quantum efficiency, and specific detectivity were calculated. Temperature-dependent measurements were fitted to diffusion-limited behavior models.
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