Temperature-Dependent DC and Small-Signal Analysis of AlGaAs/InGaAs pHEMT for High-Frequency Applications

Temperature-dependent dc and small-signal analysis have been carried out on
$0.5~\mu \text{m} \,\, \times \,\, 200$
-
$\mu \text{m}$
AlGaAs/InGaAs pseudomorphic high-electron mobility transistor over the temperature range from −40 °C to 150 °C by on-wafer S-parameter measurements up to 50 GHz. The thermal behavior of dc and equivalent circuit parameters along with their temperature coefficients was analyzed and reported for the first time using the same device. Most of these parameters show a negative trend with temperature, such as drain–source output current
$I_{\mathrm{ ds}}$
, extrinsic transconductance
$g_{m}$
, effective electron velocity
${v}_{\mathrm{ eff}}$
, threshold voltage
$V_{T}$
, Schottky barrier height
$\phi _{b}$
, gate–drain capacitance
$C_{\mathrm{ gd}}$
, drain–source capacitance
$C_{\mathrm{ ds}}$
, intrinsic transconductance
$g_{\mathrm{ mo}}$
, cutoff frequency
$f_{t}$
, and maximum frequency
$f_{\mathrm{ max}}$
. On the other hand, Two-dimensional electron gas sheet carrier density
$n_{s}$
, ON-resistance
$R_{\mathrm{\scriptscriptstyle ON}}$
, series resistance
$R_{\mathrm{ series}}$
, terminal resistances (
$R_{g}$
,
$R_{s}$
, and
$R_{d})$
, output resistance
$R_{\mathrm{ ds}}$
, input resistance
$R_{i}$
, gate–source capacitance
$C_{\mathrm{ gs}}$
, and intrinsic delay time
$\tau $
show a positive trend with temperature. The results provide some valuable insights for future design optimizations of advanced GaAs-based Monolithic microwave integrated circuits.