The paper describes design and application of foil based directly coupled inductor for two phase DC-DC converter with GaN transistors. The main advantages of the interleaved multiphase DC-DC converters over single-phase converters are reduced current stress and reduced output current ripple. Low on state resistances and low switching losses of GaN transistors allows increase current without significant increase in losses but anyway for higher switching frequencies some soft switching techniques and specific magnetics components are needed. The integrated magnetic structure can be used to achieve higher power density. The paper shows that foil based directly coupled inductor can be an option when designing such converter. PSIM software and FEMM simulation software based results are given and experimental tests are provided. It is concluded that directly coupled inductor is worth considered when designing interleaved high frequency converter, further research is needed to introduce best soft switching method for transistors and further optimize magnetics.