We report the electrical characterization of GaAsPiNjunction diodes grown over the sidewalls of patterned trenches by atomic layer epitaxy. The diodes exhibit excellent rectifying behavior demonstrating that high quality GaAs was grown on the entire trench structure including sidewalls and corners. The sidewall material is characterized electrically through reverse bias diode leakage from thermal generation in the depletion region. 2‐&mgr;m‐deep trenches contribute a leakage current of less than 60 &mgr;A/cm2of sidewall area under 1 V reverse bias at 144 °C, which is satisfactory for most device applications.