Real-time monitoring of resonant-tunneling diode growth using spectroscopic ellipsometry

We report in situ growth monitoring of pseudomorphic AlAs/In0.53Ga0.47As/InAs resonant-tunneling diodes (RTDs) using spectroscopic ellipsometry. A phase-modulated spectroscopic ellipsometer was triggered synchronously with 20 rpm substrate rotation of the III–V molecular beam epitaxy system. Postgrowth data analysis yielded layer thicknesses which were compared with the electrical characteristics of the processed RTDs. A sample set of 28 RTDs included designed variations in eight growth variables and provided for a linear model fit to the RTD peak current, peak voltage, and valley current I–V characteristics. The I–V characteristics are sensitive to the thickness of the AlAs, InAs, and InGaAs layers.