High-performance, metamorphic InxGa1-xAs tunnel diodes grown by molecular beam epitaxy

• Published in: IEEE electron device letters 2003-10, Vol.24 (10), p.613-615
• Main Authors: Kwon, O., Jazwiecki, M.M., Sacks, R.N., Ringel, S.A.
• Format: Article
• Language: English
• Subjects: Capacitive sensors; Current density; Diodes; Electric resistance; Indium gallium arsenide; Indium phosphide; Molecular beam epitaxial growth; Molecular beam epitaxy; Photonic band gap; Photovoltaic cells; Voltage
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2003.817380

Thin In/sub x/Ga/sub 1-x/As tunnel junction diodes having compositions from x=0.53 to 0.75 that span a range of bandgap energies from 0.74 to 0.55 eV, were grown on InP and metamorphic, step-graded In/sub x/Al/sub 1-x/As/InP substrates using molecular beam epitaxy and evaluated in the context of thermophotovoltaic (TPV) applications. Both carbon and beryllium were investigated as acceptor dopants. Metamorphic tunnel diodes with a bandgap of 0.60 eV (x=0.69) using carbon acceptor doping displayed highest peak current densities, in excess of 5900 A/cm/sup 2/ at a peak voltage of 0.31 V, within a 200 /spl Aring/ total thickness tunnel junction. Identically doped lattice-matched tunnel diodes with a bandgap of 0.74 eV exhibited lower peak current densities of approximately 2200 A/cm/sup 2/ at a higher peak voltage of 0.36 V, consistent with the theoretical bandgap dependence expected for ideal tunnel diodes. Specific resistivities of the 0.60 eV bandgap devices were in the mid-10/sup -5/ /spl Omega/-cm/sup 2/ range. Together with their 200 /spl Aring/ total thickness, the electrical results make these tunnel junctions promising for TPV applications where low-resistance, thin metamorphic tunnel junctions are desired.