Electric field directed assembly of an InGaAs LED onto silicon circuitry

We demonstrate an electrophoretic process for assembling very small devices on a silicon circuit. A 20-μm diameter InGaAs LED was fabricated and then released from the substrate by etching a sacrificial layer underneath the diode structure. The diode, placed into a buffer solution over the silicon circuit, was positioned onto the circuit's tin/lead contact electrodes by biasing the contacts to establish an electrophoretic current in the buffer solution. Following removal from the buffer solution, the assembly was heated to reflow the solder. Circuit formation and LED activation is demonstrated by forward biasing the LED using the silicon circuit's contacts.