The low-pressure MOVPE-grown p-InGaAs-on-n-InP and n-InP-on-p-InGaAs diodes were characterized by I-V and C-V measurements to study the effects of the growth conditions on the heterointerface. The obtained band discontinuity in the conduction band Delta E-c ranged from 0.19 to 0.32 eV. It was found that Delta E-c was very sensitive to the growth interruption at the InP/InGaAs heterointerface. The n-InP-on-p-InGaAs diodes tend to show higher Delta E-c than the p-InGaAs-on-n-InP diodes. The decreased Delta E-c at InGaAs-on-InP heterointerface might be attributed to the graded layer of InGaAsP formed by intermixing at the interface. It is concluded from the estimated Delta E-c that the InP-on-InGaAs heterointerface is more abrupt than the InGaAs-on-InP heterointerface. An improvement of the InGaAs-on-InP heterointerface is mandatory for fabrication of high-performance double heterojunction bipolar transistors with InP collector layers. (C) 2009 Elsevier B.V. All rights reserved.