Characteristics of InAlAs/InP and InAlP/GaAs wet oxidation layers were measured for the first time. These oxidation layers can be a current blocking or an optical confining layer in laser diodes. These layers were well made at 500-575 degrees C. The oxidation rates at 525 degrees C are approximately 340 nrn/h and 120 mn/h for InAlAs and InAlP oxides, respectively. The refractive index are 1.82-1.90 for InAlAs oxide and 1.565-1.595 for InAlP oxide between 0.6 pm and 1.65 mu m wavelength. The characteristics are not much varied with processing temperatures except the oxidation rate. And a 200 nni thick InAlAs oxidation layer has a current-voltage characteristic that currents rapidly flow at about 10 V, which is much lower than that of SiO2. (C) 2006 Elsevier Ltd. All rights reserved.