Kenichi Nakano

Wet Chemical Digital Etching of GaAs at Room Temperature

A new room temperature wet chemical digital etching technique for GaAs is presented which uses hydrogen peroxide and an acid in a two‐step etching process to remove GaAs in approximately 15 A increments. In the first step, GaAs is oxidized by 30% hydrogen peroxide to form an oxide layer that is diffusion limited to a thickness of 14 to 17 A for time periods from 15 to 120 s. The second step removes this oxide layer with an acid that does not attack unoxidized GaAs. These steps are repeated in succession until the desired etch depth is obtained. Experimental results are presented for this digital etching technique demonstrating the etch rate and process invariability with respect to hydrogen peroxide and acid exposure times.

Thermal studies on heterostructure bipolar transistors using electroluminescence

We have studied electroluminescence (EL) emission from fully fabricated GaAs based heterostructure bipolar transistors. The EL emission occurs due to minority carrier injection into the base and collector layers. Under normal device operation, i.e. with reverse bias on the collector/base junction, collector emission does not occur since holes are not injected into this layer. In this case, only base emission is observed. When a forward bias is applied to the base/collector junction, EL from both the collector and the base is observed. The spectral characteristics of the two EL signals are different since the bandgap of the heavily p-doped base is smaller than that of the lightly n-doped collector. Since the bandgap depends strongly on temperature, the spectral characteristics are used to determine the heating of the HBT due to power dissipation.