The layout is most critical regardless if the device is e-mode, d-mode or cascode configuration.  All of these devices switch extremely fast and therefore the parasitic inductance of the layout must be as small as possible, in the range of 0.4 nH to 2.0 nH is desirable.

What are the projections for future GaN products?

Fig. 4 is EPC’s projection of the future of GaN devices. When originally introduced in 2010, devices were rated at 40 to 200 V and 500 Mhz switching speed. Recent introductions by EPC raised the speed up to 3 GHz for devices rated at 40 V, 65 V and 100 V and on-resistance ranging from 125 mΩ to 530 mΩ. The company also expects GaN transistors to eventually operate at 600 V and it expects more functions per chip.

GaN Projections
Fig. 4 - The future of GaN transistors indicates the development of faster and higher voltage devices.