The conduction properties of GeGaAs_1-xP_x n-n heterojunctions

Abstract

n-type Ge has been grown epitaxially on GaAs1-xPx substrates of 4 × 1017 cm-3 donors at 360°C. The substrates have 〈111〉 orientation and a composition range of x = 0, 0·1 and 0·3. Junctions made with x = 0 or 0·1 exhibit diode behaviour that can be interpreted by the metal-semiconductor emission theory modified to take into account the effects of both electron tunnelling and voltage distribution between the semiconductors. The barrier heights have been found to be 0·62 and 0·53 V for the A- and B-surface of substrates with x = 0·1 and 0·50 V and 0·43 V correspondingly with x = 0. The apparent barriers at zero bias are smaller than these values by about 0·2 V due to tunnelling reduction. For substrates with x = 0·3, various measurements tend to suggest a structure of back-to-back diodes. The effect of interface states, as likely produced by the relatively large lattice mismatch in this case (>1 per cent), is believed to be responsible for this structure. © 1965.