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Pulsed laser deposition of barium hexagonal ferrite grown on semiconductor substrates

            In recent years, Si and GaAs have been pushed to their theoretical limits to make smaller and faster devices. But the world never stops its pace with the promising solution of SiC and GaN wide band materials. With a high saturated drift velocity (~2.7* 107 cm/s), wide band gap (3.03 eV), and high breakdown electric field strength (2.4 x 106 V/cm) , SiC, like GaN, holds unique potential as a substrate for the next generation of high-temperature, high-frequency, and high-power electronics.

         In the ferrite device community, a longstanding goal is the integration of nonreciprocal ferrite microwave devices with semiconductor platforms. More specifically, the aim is to develop planar ferrite devices that send, receive and manipulate electromagnetic radiation and efficiently couple these devices to CMOS-based integrated circuits. Different strategies have been tried and are currently ongoing. During the 1990’s much research focused on the integration of spinel ferrites with GaAs substrates. These efforts failed largely because of the high temperature processing of the ferrites leads to the degradation of the GaAs. Since 1990s, ferrite materials and device development has progressed to higher frequency operations (K- and Q-band) based on hexaferrite materials (e.g. BaFe12O19). The reliance of hexaferrite materials do not alleviate the dependence on high temperature processing. However, new wide bandgap semiconductors (SiC and GaN) have evolved to now offer new opportunities for ferrite/semiconductor materials integration. The wide bandgap semiconductors are stable at much higher temperatures than GaAs and may hold for the integration of ferrite materials with semiconductor electronics.
In our MMMIC lab, we are now forcusing on the epitaxial growth of Ba-hexaferrite on SiC and GaN substrates using PLD, LPE and other film techniques; An essential first step to the next generation device Integration.

BaM_XRD

Fig. 1. X-ray diffraction pattern for Ba-hexaferrite (M-type) film grown at 20 mTorr oxygen pressure. All significant diffraction features are referenced to (0,0,2n) indices having space group P6/mmc.

BaM_AFM

Fig. 2. Atomic force microscopy images processed in tapping mode illustrating hexagonal crystals oriented with c-axis perpendicular to the film plane.

BaM_VSM 

Fig. 3. Hysteresis loops obtained by vibrating sample magnetometry of films grown by PLD at a) 20 mTorr and b) 200 mTorr oxygen pressure.

 

 
 
         
Maintained by Aria Yang, Last updated on Nov. 3, 2008