Investigation of Epitaxial Lift-Off Gallium Arsenide and Langmuir-Blodgett Films for Optoelectronic Device Applications

Epitaxial lift-off (ELO), a technique of removing an epitaxially grown GaAs layer from its growth substrate by selective etching of an AlAs sacrificial layer, is described for field-effect transistor fabrication independent of the GaAs growth substrate. Metal Semiconductor Field-Effect Transistors (MESFETs) and High Electron Mobility Transistors (HEMTs) fabricated on silicon and sapphire substrates using ELO are investigated. A 0.1 μm gate length depletion mode MESFET made on silicon exhibited a unity current gain frequency f_{ rm t} = 34 GHz. Excellent device isolation with subpicoampere leakage currents is obtained. A high input impedance amplifier has been implemented on silicon substrate using ELO GaAs MESFETs. The amplifier had an input RC time constant limited bandwidth of 500 MHz. Results of investigation of a novel source of cadmium and zinc diffusion for shallow p^ {+}-n junction fabrication in In _{0.53}Ga_{0.47 }As/InP are also presented. Langmuir-Blodgett (LB) deposited monolayers of Cadmium and Zinc arachidate have been used as a source of Cd and Zn dopants in InGaAs/InP. This new source provides precise control of the dopant dose through the number of LB film monolayers deposited and it is also a safer method of handling toxic Cd. The LB film can be patterned by lift-off for a patterned diffusion without a mask. Highly doped (N_{ rm a}= 2-4 times 10^{19} cm^ {-3}), shallow (0.1-0.4 mu m) p^{+}-n junctions have been obtained. Junction field-effect transistors (JFETs) and PIN photodetectors have been fabricated as a demonstration of the usefulness of the technique. A PIN photodetector had a 100 pA dark current at -5 V DC bias and a bandwidth of 2 GHz. A new technique for fabricating optoelectronic integrated circuit (OEIC) photoreceivers for 1.3-1.55 μm wavelength optical communication has also been proposed. The proposed OEIC uses ELO GaAs MESFETs and InGaAs/InP PIN photodetectors.