The effects of non-constant epilayer doping profiles on charge injection in acoustic charge transport devices

The effects of spatial variations in the epilayer doping density on charge injection in ACT (acoustic charge transport) devices are investigated. The model used to perform the charge injection simulations is based on a simplification of the model proposed by E. G. Bogus (1987). Spatial variations in the epilayer doping density offer a method of increasing injected charge packet compression. Such charge packet compression is thought to increase charge transfer efficiency. Charge injection simulations are performed for the cases of linear- and Gaussian-shaped doping profiles, and the results are compared to the case of constant epilayer doping. The Gaussian profile was superior to the constant and linear profiles in terms of linearity of the channel-current-input-voltage relationship and exhibited a somewhat higher input transconductance. In terms of sampling time variations, however, the constant doping profile remained better than any of the spatial variations examined