50-nm E-mode In[subscript 0.7]Ga[subscript 0.3]As PHEMTs on 100-mm InP substrate with f[subscript max] > 1 THz

Abstract

We have demonstrated 50-nm enhancement-mode (E-mode) In[subscript 0.7]Ga[subscript 0.3]As PHEMTs with f[subscript max] in excess of 1 THz. The devices feature a Pt gate sinking process to effectively thin down the In[subscript 0.52]Al[subscript 0.48]As barrier layer, together with a two-step recess process. The fabricated device with L[subscript g] = 50-nm exhibits V[subscript T] = 0.1 V, g[subscript m,max] = 1.75 mS/μm, f[subscript T] = 465 GHz and f[subscript max] = 1.06 THz at a moderate value of V[subscript DS] = 0.75 V. In addition, we have physically modeled the abnormal peaky behavior in Mason's unilateral gain (U[subscript g]) at high values of VDS. A revised small signal model that includes a shunting R[subscript gd-NDR] with negative value successfully describes the behavior of the device from 1 to 67 GHz.