\begin{tikzpicture}[scale=1]

\pgfmathsetmacro{\tkW}{8}               % Total width
\pgfmathsetmacro{\tkH}{5}               % Total height
% left
\pgfmathsetmacro{\tkLx}{0}              % Start
\pgfmathsetmacro{\tkLW}{2}              % Right width
\pgfmathsetmacro{\tkLyshift}{0.0}      % y-shift
\pgfmathsetmacro{\tkLBendH}{0}        % Band bending height
\pgfmathsetmacro{\tkLBendW}{0}    % Band bending width
\pgfmathsetmacro{\tkLEV}{4.0+\tkLyshift}% Vacuum energy
\pgfmathsetmacro{\tkLEf}{2.5+\tkLyshift}% Fermi level energy
% right
\pgfmathsetmacro{\tkRx}{4}          % Left start
\pgfmathsetmacro{\tkRW}{\tkW-\tkRx}     % Left width
\pgfmathsetmacro{\tkRyshift}{0}         % y-shift
\pgfmathsetmacro{\tkRBendH}{0.5}         % Band bending height
\pgfmathsetmacro{\tkRBendW}{\tkRW/4}     % Band bending width
\pgfmathsetmacro{\tkREv}{0.7+\tkRyshift}% Valence band energy
\pgfmathsetmacro{\tkREc}{2.5+\tkRyshift}% Conduction band energy
\pgfmathsetmacro{\tkREV}{4.0+\tkRyshift}% Vacuum energy
\pgfmathsetmacro{\tkREf}{2.0+\tkRyshift}% Fermi level energy

% materials
\draw[sc metal] (0,0) rectangle (\tkLW,\tkH);
\node at (\tkLW/2,\tkH-0.2) {\GT{metal}};
\path[sc n type] (\tkRx,0) rectangle (\tkW,\tkH);
\node at (\tkRx+\tkRW/2,\tkH-0.2) {\GT{n-type}};

\drawAxes

% right bands
\path[sc occupied] (\tkRx, 0) -- \rightBand{}{\tkREv} -- (\tkW, 0) -- cycle;
\draw[sc band con] \rightBand{$\Econd$}{\tkREc};
\draw[sc band val] \rightBand{$\Evalence$}{\tkREv};
\draw[sc band vac] (0,\tkLEV) -- \rightBand{$\Evac$}{\tkREV};
\draw[sc fermi level] \rightBand{$\Efermi$}{\tkREf};
% left bands
\path[sc occupied] (0,0) rectangle (\tkLW,\tkLEf);
\draw[sc fermi level] \leftBand{$\Efermi$}{\tkLEf};

% work functions
\drawDArrow{\tkLW/2}{\tkLEf}{\tkLEV}{$e\Phi_\txM$}
\drawDArrow{\tkRx+\tkRW*2/3}{\tkREf}{\tkREV}{$e\Phi_\txS$}
\drawDArrow{\tkRx+\tkRW*1/3}{\tkREc}{\tkREV}{$e\chi$}

\end{tikzpicture}

