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Selective Gate Recessing of GaAs/AIGaAs/lnGaAs Pseudomorphic HEMT Structures Using BCl3 Plasmas

  • T. E. Kazior (a1) and B. I. Patel (a1)

Abstract

Wet chemical gate recessing of GaAs based devices suffers from poor control and uniformity of the recess etch depth. Electrical variability can be particularly severe for heterojunction devices that contain thin highly doped layers. This problem can be addressed by the use of etch stop layers and the appropriate etch chemistry. In this paper, results on the selective plasma etching of GaAs from InGaAs and AIGaAs etch stop layers are presented. Using a BCl3 plasma, GaAs layers were removed from thin lnxGa(1-X)As (0.12<x<0.25) layers with selectivities >1000 to 1 due to the poor volatility of indium chlorides. With the addition of SFe, the etch process becomes selective to AlxGa (1-X)As due to the formation of a non-volatile AlFX layer. By the judicious choice of etch conditions (high pressure and low power resulting in low DC bias and optimal BCl3/SF6 ratio), isotropie etch profiles with minimal substrate damage and GaAs to Al0.25Ga0.75As selectivities >1000 to 1 have been achieved. Using these etch conditions, pseudomorphic HEMT wafers were selectively plasma gate recessed yielding saturated current uniformities across a 3 inch wafer of <±1.0mA/100μm of gate periphery. Device characteristics and uniformities that are dependent upon the material structure and epitaxial layer thickness and dopant uniformities rather than upon the gate recess process are realized.

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Selective Gate Recessing of GaAs/AIGaAs/lnGaAs Pseudomorphic HEMT Structures Using BCl3 Plasmas

  • T. E. Kazior (a1) and B. I. Patel (a1)

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