Comparison of InGaAs/InAlAs electroabsorption modulator structures on (100) and (111) InP substrates

The MBE growth and properties of InGaAs/InAlAs heterostructures on vicinal (111)B InP substrates have been investigated. Electroabsorption modulator pin MQW heterostructures were grown on both (100) and vicinal (111)B InP substrates, pin diodes were processed and their photocurrent spectra at 300 K were compared. The spectra of (100) structures exhibited many intense excitonic transitions and applied reverse bias resulted to strong red shift of the absorption edge. The photocurrent spectra of similar (111) structures, however, appeared rather featureless with less abrupt absorption edge. These results on (111) are related to crystal disorder and quantum well variations resulting from InAlAs surface step-bunching and InGaAs, InAlAs compositional modulations.