Polarization Induced Graded AlGaN p-n Junction grown by MBE

Wide bandgap lll-V nitride semiconductors have attracted a large interest in recent years due to their applications in high power and opto-electronic devices. However, the development of nitride based UV optical devices has been limited due to the difficulties in growth and processing of good quality p-type and n-type layers of high Al composition AIGaN, where both acceptor and donor dopants have very high activation energies. High acceptor activation energies of Mg acceptor atoms (~160 meV) combined with low mobilities of holes in nitrides result in very resistive p-type layers, limiting the optical and high frequency performance of any bipolar device. Recently we have demonstrated the ability to produce polarization-induced bulk n-type doping in AIGaN graded slabs . By using the polarization charges found in nitride semiconductors it is possible to controllably induce bulk doping in graded slabs without the introduction of any impurity dopants. By inverting the grading direction during growth the polarization charges will also be inverted, resulting in an induced bulk p-type doping without the need to dope the crystal with Mg atoms.