Demonstration of nitrogen carrier gas in MOVPE for InP/InGaAs-based high frequency and optoelectronic integrated devices

InAlAs as a barrier or buffer material has many disadvantages compared to InP such as ageing, DX-centers, lack of etch control and need for surface passivation. Its use in high frequency devices is mainly historical: it is deposited by MBE, a technique which in the past was not well suited for P-based materials but well suited for obtaining homogeneous highly resistive (Al-containing) buffer layers as needed in HEMT-structures. The use of InP as the barrier layer for HEMT-structures requires highly resistive substrates and buffer layers, which are preferentially deposited by MOVPE. In this paper we will report on the suitability of (1) InP as the barrier material, (2) an innovative MOVPE process for its deposition and (3) the use of newly developed highly resistive InP wafers for high frequency and optoelectronic integrated devices. To enhance layer homogeneity, the structures were deposited in a conventional MOVPE system using nitrogen as the carrier gas.