Dependence of the DC, and the RF Characteristics of InGaAs /InP Single Heterojunction Bipolar Transistors on the Collector Layer Thickness

We have experimentally compared to different collector layer thickness and analyzed the dependence of the dc and the RF characteristics of the non self-aligned single heterojunction bipolar transistors (SHBTs) on the collector layer’s thickness. For this comparative study, we fabricated InGaAs/InP SHBTs with collector layer thicknesses of 3500 °A (sample A) and 5000 °A (sample B). The emitter size of SHBT was set to be 1.2 × 6 μm2. We investigated the dependence of the cut-off frequency (fT ) and the maximum oscillation frequency (fmax) on the collector current for SHBTs with different collector thicknesses and the same doping density to clarify the transit time and the charging time for the InGaAs/InP SHBT. In the sample A, maximum fmax and fT were measured to be 176 GHz and 143 GHz, respectively at VCE = 1.5 V and Ic = 12 mA. In sample B, the maximum fmax and fT were measured to be 126 GHz and 127 GHz, respectively at VCE = 1.5 V and Ic = 12 mA. The dc current gain () and the breakdown voltage (BVceo) at IB = 1 mA were 25 and 6 V in sample A, respectively. For sample B, the dc current gain () and the breakdown voltage (BVceo) at IB = 1 mA were 26 and 8 V, respectively. The offset voltages, Vce off.set, were independent of the collector layer thickness, and were about 0.11 V for sample A and sample B. The experimental results manifest that it takes a shorter time for charging and transition of electrons in InGaAs/InP SHBTs with thinner collector layers. KCI Citation Count: 1