Non-destructive mapping of doping and structural composition of MOVPE-grown high current density resonant tunnelling diodes through photoluminescence spectroscopy

• We report on wafer-level uniformity of InP based RTDs grown by MOVPE.
• Absolute doping concentration measured through photoluminescence (PL) spectroscopy.
• Low temperature PL emission from the quantum well (QW) and contact layers identified.
• Doping, alloy and QW uniformity and perfection non-destructively mapped.
• Our observations are confirmed with eCV profiling, SIMS and HRXRD.

We report on photoluminescence (PL) characterisation of metal-organic vapour phase epitaxy (MOVPE) grown high current density (~700 kA/cm2) InGaAs/AlAs/InP based resonant tunnelling diodes (RTDs) for terahertz emission. The PL mapping we describe allows important information about doping level and uniformity, ternary alloy composition and uniformity, and uniformity of quantum well thickness to be deduced. PL as a function of doping concentration is studied for InGaAs test layers at low temperatures and correlated to secondary-ion mass spectroscopy (SIMS) and electrochemical capacitance–voltage (eCV) profiling to provide non-destructive mapping of doping over the wafer. For the RTD structures, we utilise eCV as a selective etch tool to identify the origin of low temperature PL emission from the quantum well (QW) and the highly doped contact layers. PL mapping of the RTD wafer at low temperatures is shown to allow the assessment of variations in InGaAs alloy composition and QW thickness. Details of the growth process are discussed and confirmed using high resolution X-ray diffraction (HRXRD) crystallography. The rapid non-destructive characterisation and wafer mapping of these structures promises a route to future growth optimisation of such structures.