A novel method is presented for detecting confined energy states in quantum dots embedded in a junction space charge region, where the reverse bias is used to discharge the initially occupied energy levels. By determining the temperature derivative of junction capacitance as a function of bias voltage and temperature, spectra are obtained with peaks revealing the existence of electron states in InGaAs/GaAs quantum dots structure grown by molecular beam epitaxy. The method is compared with admittance based techniques and theory used earlier for interpretation of experimental data.